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Archive-name: linux/howto/scsi
Last-modified: 28 April 1996
Version: 2.27

Copyright 1994, 1995, 1996, Drew Eckhardt

    This documentation is free documentation; you can redistribute it and/or
    modify it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This documentation is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this documentation; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

That said, I'd appreciate it if people would ask me <[e-mail]>
if there's a newer version available before they publish it.  When people
publish outdated versions, I get questions from users that are answered
in newer versions, and it reflects poorly on the publisher.  I'd also prefer
that all references to free distribution sites, and possibly competing
distributions/products be left intact.

IMPORTANT :

BUG REPORTS OR OTHER REQUESTS FOR HELP WHICH FAIL TO FOLLOW THE PROCEDURES
OUTLINED IN SECTION 2 WILL BE IGNORED.

This HOWTO covers the Linux SCSI subsystem, as implemented in Linux
kernel revision 1.2.10 and newer alpha code.  Earlier revisions of the
SCSI code are _unsupported_, and may differ significantly in terms of the
drivers implemented, performance, and options available.

For additional information, you may wish to join the linux-scsi mailing list
by mailing [e-mail] with the line

    subscribe linux-scsi

in the text.  You can unsubscribe by sending mail to the same address and
including

    unsubscribe linux-scsi

in the text.

Once you're subscribed, you can send mail to the list at

    [e-mail]

I'm aware that this document isn't the most user-friendly,
and that there may be inaccuracies and oversights.  If
you have constructive comments on how to rectify the situation
you're free to mail me about it.

Table of contents
Section 1             Common Problems
    Section 1.1            General Flakiness
    Section 1.2         The kernel command line
    Section 1.3           A SCSI device shows up at all possible IDs
    Section 1.4         A SCSI device shows up at all possible LUNs
    Section 1.5            You get sense errors when you know the
                    devices are error free
    Section 1.6            A kernel configured with networking does
                    not work.
    Section 1.7              Device detected, but unable to access.
    Section 1.8            Sometimes the scsi subsystem locks up
                    completely.
    Section 1.9         Configuring and building the kernel
    Section 1.10        LUNS other than 0 don't work

Section 2            Reporting Bugs
    Section 2.1            Capturing messages
    Section 2.2            Locating the source of a panic()

Section 3            Modules
    Section 3.1            General information.
    Section 3.2            Status of modules under 1.2 kernels.
    Section 3.3            Status of modules under 1.3 kernels.

Section 4            Hosts
    Section 4.1            Supported and Unsupported Hardware
    Section 4.1.1        Multiple host adapters
    Section 4.2            Common Problems
    Section 4.3            Adaptec 152x, 151x, 1505, 282x,
                    Sound Blaster 16 SCSI,
                    SCSI Pro, Gigabyte, and other AIC
                    6260/6360 based products (Standard)
    Section 4.4            Adaptec 154x, Adaptec 1640, AMI FastDisk VLB,
                    (DTC 329x may also work), (Standard)
    Section 4.5            Adaptec 174x (Standard)
    Section 4.6            Adaptec 274x, 284x (Standard), 294x (ALPHA)
    Section 4.7            Allways IN2000 (ALPHA)
    Section 4.8            BusLogic MultiMaster Host Adapters
    Section 4.9            BusLogic FlashPoint Host Adapters
    Section 4.10        EATA: DPT Smartcache, Smartcache Plus,
                    Smartcache III (Standard)
    Section 4.11        Future Domain 16x0 with TMC-1800, TMC-18C30,
                    TMC-18C50, or TMC-36C70 chip (Standard)
    Section 4.12        Generic NCR5380 / T130B (Standard)
    Section 4.13        NCR53c8xx rel5 (Standard), rel10+ (ALPHA)
    Section 4.14        Seagate ST0x/Future Domain TMC-8xx/TMC-9xx
                    (Standard)
    Section 4.15         PAS16 (Standard)
    Section 4.16        Trantor T128/T128F/T228 (Standard)
    Section 4.17        Ultrastor 14f, 24f,  34f (Standard)
    Section 4.18        Western Digital 7000 (Standard)
    Section 4.19        AM53/79C974 (ALPHA)
    Section 4.20        qlogic (STANDARD)

Section 5            Disks
    Section 5.1         Supported and Unsupported Hardware
    Section 5.2         Common Problems
    Section 5.3            Device Files
    Section 5.4            Partitioning
    Section 5.5            Disk Geometry

Section 6             CD ROMs
    Section 6.1            Supported and Unsupported Hardware
    Section 6.2            Common Problems
    Section 6.3            Device Files

Section 7            Tapes
    Section 7.1            Supported and Unsupported Hardware
    Section 7.2            Common Problems
    Section 7.3            Device Files

Section 8            Generic
    Section 8.1            Supported and Unsupported Hardware
    Section 8.2            Common Problems
    Section 8.3            Device Files

Section 9            Buyers' Guide
    Section 9.1         Transfer types
    Section 9.2         Scatter/gather
    Section 9.3         Mailbox vs. non-mailbox
    Section 9.4            Bus types
    Section 9.5            Multiple devices
    Section 9.6            SCSI-I, SCSI-II, FAST and WIDE options, etc.
    Section 9.7            Driver feature comparison
    Section 9.8              Board comparison
    Section 9.9            Summary

Section 10
    Section 10.1        Assignment of minor numbers.

Section 1 : Common Problems

This section lists some of the common problems that people
have.  If there is not anything here that answers your questions, you
should also consult the sections for your host adapter and the devices
in that are giving you problems.

Section 1.1 : General Flakiness
    If you experience random errors, the most likely causes are
    cabling and termination problems.

    Some products, such as those built arround the newer NCR
    chips, feature digital filtering and active signal negation,
    and aren't very sensitive to cabling problems.

    Others, such as the Adaptec 154xC, 154xCF, and 274x, are _extremely_
    sensitive and may fail with cables that work with other systems.

    I reiterate : some host adapters are _extremely_ sensitive to
    cabling and termination problems and therefore, cabling and
    termination should be the first things checked when there are
    problems.

    To minimize your problems, you should use cables which

        1.  Claim SCSI-II compliance
    2.  Have a characteristic impedance of 132 ohms
    3.  All come from the same source to avoid impedance mismatches
    4.  Come from a reputable vendor such as Amphenol

    Termination power should be provided by _all_ devices on
    the SCSI bus, through a diode to prevent current backflow,
    so that sufficient power is available at the ends of the cable
    where it is needed.  To prevent damage if the bus is shorted,
    TERMPWR should be driven through a fuse or other current
    limiting device.

    If multiple devices, external cables, or FAST SCSI 2 are used,
    active or forced perfect termination should be used on both ends
    of the SCSI bus.

    See the Comp.Periphs.Scsi FAQ (available on tsx-11 in
    pub/linux/ALPHA/scsi) for more information about active
    termination.

Section 1.2 : The kernel command line

    Other parts of the documentation refer to a "kernel command line".

    The kernel command line is a set of options you may specify
    from either the LILO : prompt after an immage name, or in the
    append field in your LILO configuration file (LILO .14
    and newer use /etc/lilo.conf, older versions use /etc/lilo/config).

    Boot your system with LILO, and hit one of the alt, control, or
    shift keys when it first comes up to get a prompt.  LILO
    should respond with

        :

    At this prompt, you can select a kernel image to boot, or list
    them with ?.  Ie

        :?

        ramdisk floppy harddisk

    To boot that kernel with the command line options you have
    selected, simply enter the name followed by a white space delimited
    list of options, terminating with a return.

    Options take the form of

        variable=valuelist

    Where valuelist may be a single value or comma delimited list
    of values with no whitespace.  With the exception of root device,
    individual values are numbers, and may be specified in either
    decimal or hexadecimal.

    Ie, to boot linux with an Adaptec 1520 clone not recognized
    at bootup, you might type

        :floppy aha152x=0x340,11,7,1

    If you don't care to type all of this at boot time, it is also
    possible to use the LILO configuration file "append" option
    with LILO .13 and newer.

    Ie,
        append="aha152x=0x340,11,7,1"


Section 1.3 :  A SCSI device shows up at all possible IDs

    If this is the case, you have strapped the device at the same
    address as the controller (typically 7, although some boards
    use other addresses, with 6 being used by some Future Domain
        boards).

    Please change the jumper settings.

Section 1.4 :  A SCSI device shows up at all possible LUNs

    The device has buggy firmware.

    As an interim sollution, you should try using the kernel
    command line option

        max_scsi_luns=1

    If that works, there is a list of buggy devices
    in the kernel sources in drivers/scsi/scsi.c in the variable
    blacklist.  Add your device to this list and mail the patch
    to Linus Torvalds <[e-mail]>.

Section 1.5 :  You get sense errors when you know the devices are error free

    Sometimes this is caused by bad cables or impropper termination.

    See Section 1.1 : General Flakiness

Section 1.6 :  A kernel configured with networking does not work.

    The auto-probe routines for many of the network drivers
    are not passive, and will interfere with operation with some
    of the SCSI drivers.

Section 1.7 :  Device detected, but unable to access.

    A SCSI device is detected by the kernel, but you are unable to
    access it - ie mkfs /dev/sdc, tar xvf /dev/rst2, etc fails.

    You don't have a special file in /dev for the device.

    Unix devices are identified as either block or character (block
    devices go through the buffer cache, character devices do not) devices,
    a major number (ie which driver is used - block major 8 corresponds
    to SCSI disks) and a minor number (ie which unit is being accessed
    through a given driver - ie character major 4, minor 0 is the first
    virtual console, minor 1 the next, etc).  However, accessing devices
    through this separate namespace would break the unix/Linux metaphor of
    "everything is a file," so character and block device special files
    are created under /dev.  This lets you access the raw third SCSI disk
    device as /dev/sdc, the first serial port as /dev/ttyS0, etc.

    The preferred method for creating a file is using the MAKEDEV script -
    cd /dev

    and run MAKEDEV (as root) for the devices you want to create - ie

    ./MAKEDEV sdc

    wildcards "should" work - ie

    ./MAKEDEV sd\*

    "should" create entries for all SCSI disk devices (doing this should
    create /dev/sda through /dev/sdp, with fifteen partition entries for
    each)

    ./MAKEDEV sdc\*

    "should" create entries for /dev/sdc and all fifteen permissible
    partitions on /dev/sdc, etc.

    I say "should" because this is the standard unix behavior - the MAKEDEV
    script in your installation may not conform to this behavior, or may
    have restricted the number of devices it will create.

    If MAKEDEV won't do the right magic for you, you'll have to create the
    device entries by hand with the mknod command.

    The block/character type, major, and minor numbers are specified for the
    various SCSI devices in Subsection 4 : Device Files in the appropriate
    section.

    Take those numbers, and use (as root)

    mknod /dev/device b|c major minor

    ie -

    mknod /dev/sdc b 8 32
    mknod /dev/rst0 c 9 0

Section 1.8 :   SCSI System Lockups

    This could be one of a number of things.  Also see the section for
    your specific host adapter for possible further solutions.

    There are cases where the lockups seem to occur when multiple devices
    are in use at the same time.  In this case, you can try contacting
    the manufacturer of the devices and see if firmware upgrades are
    available which would correct the problem.  If possible, try a
    different scsi cable, or try on another system.  This can also
    be caused by bad blocks on disks, or by bad handling of DMA by the
    motherboard (for host adapters that do DMA).  There are probably
    many other possible conditions that could lead to this type of event.

    Sometimes these problems occur when there are multiple devices in
    use on the bus at the same time.  In this case, if your host
    adapter driver supports more than one outstanding command on the bus
    at one time, try reducing this to 1 and see if this helps. If you
    have tape drives or slow cdrom drives on the bus, this might not be
    a practical solution.

Section 1.9 : Configuring and building the kernel

    Unused SCSI drivers eat up valuable memory, aggravating
    memory shortage problems on small systems because kernel
    memory is unpagable.

    So, you will want to build a kernel tuned for your
    system, with only the drivers you need installed.

    cd to /usr/src/linux

    If you are using a root device other than the current
    one, or something other than 80x25 VGA, and you are
    writing a boot floppy, you should edit the makefile,
    and make sure the

        ROOT_DEV =

    and

        SVGA_MODE =

    lines are the way you want them.

    If you've installed any patches, you may wish to guarantee that all
    files are rebuilt.  If this is the case, you should type

        make mrproper

    Irregardless of weather you ran make mrproper, type

        make config

    and answer the configuration questions.  Then run

        make depend

    and finally

        make

    Once the build completes, you may wish to update the
    lilo configuration, or write a boot floppy.  A boot floppy
    may be made by running

        make zdisk

Section 1.10 : LUNS other than 0 don't work

    Many SCSI devices are horrendously broken, lock the SCSI
    bus up solid, and do other bad things when you attempt to
    talk to them at a logical unit someplace other than zero.

    So, by default recent versions of the Linux kernel will not
    probe luns other than 0.  To work arround this, you need to
    the max_scsi_luns command line option, or recompile the kernel
    wiuth the CONFIG_SCSI_MULTI_LUN option.

    Usually, you'll put

        max_scsi_luns=8

    on your LILO command line.

    If your multi-LUN devices still aren't detected correctly after
    trying one of these fixes (as the case will be with many old
    SCSI->MFM, RLL, ESDI, SMD, and similar bridge boards),  you'll
    be thwarted by this piece of code

                  /* Some scsi-1 peripherals do not handle lun != 0.
                     I am assuming that scsi-2 peripherals do better */
                  if((scsi_result[2] & 0x07) == 1 &&
                     (scsi_result[3] & 0x0f) == 0) break;

    in scan_scsis() in drivers/scsi/scsi.c.  Delete this code,
    and you should be fine.

Section 2 : Reporting Bugs

The Linux SCSI developers don't necessarily maintain old revisions
of the code due to space constraints.  So, if you are not running the
latest publically released Linux kernel (note that many of the Linux
distributions, such as MCC, SLS, Yggdrasil, etc. often lag one or even
twenty patches behind this) chances are we will be unable to solve your
problem.  So, before reporting a bug, please check to see if it exists
with the latest publically available kernel.

If after upgrading, and reading this document thoroughly, you still
believe that you have a bug, please mail a bug report to the SCSI channel
of the mailing list where it will be seen by many of the people who've
contributed to the Linux SCSI drivers.

In your bug report, please provide as much information as possible
regarding your hardware configuration, the exact text of
all of the messages that Linux prints when it boots, when the
error condition occurs, and where in the source code the error
is.  Use the procedures outlined in Section 2.1 : Capturing
messages and Section 2.2 : Locating the source of a panic().

Failure to provide the maximum possible amount of information
may result in misdiagnosis of your problem, or developers
deciding that there are other more interesting problems to
fix.

The bottom line is that if we can't reproduce your bug, and you can't
point at us what's broken, it won't get fixed.

Section 2.1 : Capturing messages

If you are not running a kernel message logging system :

Insure that the /proc filesystem is mounted.

    grep proc /etc/mtab

If the /proc filesystem is not mounted, mount it

    mkdir /proc
    chmod 755 /proc
    mount -t proc /proc /proc

Copy the kernel revision and messages into a log file

    cat /proc/version > /tmp/log
    cat /proc/kmsg >> /tmp/log

Type CNTRL-C after a second or two.

If you are running some logger, you'll have to poke through the
appropriate log files (/etc/syslog.conf should be of some use
in locating them), or use dmesg.

If Linux is not yet bootstrapped, format a floppy diskette under DOS.
Note that if you have a distribution which mounts the root diskette off of
floppy rather than RAM drive, you'll have to format a diskette readable
in the drive not being used to mount root or use their ramdisk boot option.

Boot Linux off your distribution boot floppy, preferably in single user mode
using a RAM disk as root.

    mkdir /tmp/dos

Insert the diskette in a drive not being used to mount root, and
mount it.  Ie

    mount -t msdos /dev/fd0 /tmp/dos

    or

    mount -t msdos /dev/fd1 /tmp/dos

Copy your log to it

        cp /tmp/log /tmp/dos/log

Unmount the DOS floppy

    umount /tmp/dos

And shutdown Linux

    shutdown

Reboot into DOS, and using your favorite communications software include
the log file in your trouble mail.

Section 2.2 : Locating the source of a panic()

Like other unices, when a fatal error is encountered, Linux calls the
kernel panic() function.  Unlike other unices, Linux doesn't dump
core to the swap or dump device and reboot automatically.  Instead,
a useful summary of state information is printed for the user to
manually copy down.  Ie :

    Unable to handle kernel NULL pointer dereference at virtual address c0000004
    current->tss,cr3 = 00101000, %cr3 = 00101000
    *pde = 00102027
    *pte = 00000027
    Oops: 0000
    EIP:    0010:0019c905
    EFLAGS: 00010002
    eax: 0000000a   ebx: 001cd0e8   ecx: 00000006   edx: 000003d5
    esi: 001cd0a8   edi: 00000000   ebp: 00000000   esp: 001a18c0
    ds: 0018   es: 0018   fs: 002b   gs: 002b   ss: 0018
    Process swapper (pid: 0, process nr: 0, stackpage=001a09c8)
    Stack: 0019c5c6 00000000 0019c5b2 00000000 0019c5a5 001cd0a8 00000002 00000000
       001cd0e8 001cd0a8 00000000 001cdb38 001cdb00 00000000 001ce284 0019d001
       001cd004 0000e800 fbfff000 0019d051 001cd0a8 00000000 001a29f4 00800000
    Call Trace: 0019c5c6 0019c5b2 0018c5a5 0019d001 0019d051 00111508 00111502
       0011e800 0011154d 00110f63 0010e2b3 0010ef55 0010ddb7
    Code: 8b 57 04 52 68 d2 c5 19 00 e8 cd a0 f7 ff 83 c4 20 8b 4f 04
    Aiee, killing interrupt handler
    kfree of non-kmalloced memory: 001a29c0, next= 00000000, order=0
    task[0] (swapper) killed: unable to recover
    Kernel panic: Trying to free up swapper memory space
    In swapper task - not syncing

Take the hexidecimal number on the EIP: line, in this case 19c905, and search
through /usr/src/linux/zSystem.map for the highest number not larger than
that address.  Ie,

    0019a000 T _fix_pointers
    0019c700 t _intr_scsi
    0019d000 t _NCR53c7x0_intr

That tells you what function its in.  Recompile the source file which
defines that function file with debugging enabled, or the whole kernel
if you prefer by editing /usr/src/linux/Makefile and adding a "-g"
to the CFLAGS definition.

    #
    # standard CFLAGS
    #

Ie,

    CFLAGS = -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer -pipe

becomes

    CFLAGS = -g -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer -pipe

Rebuild the kernel, incrementally or by doing a

    make clean
    make

Make the kernel bootable by creating an entry in your /etc/lilo.conf
for it

    image = /usr/src/linux/zImage
    label = experimental

and re-running LILO as root, or by creating a boot floppy

    make zImage

Reboot and record the new EIP for the error.

If you have script installed, you may want to start it, as
it will log your debugging session to the typescript file.

Now, run

    gdb /usr/src/linux/tools/zSystem

and enter

    info line *<your EIP>

Ie,
    info line *0x19c905

To which GDB will respond something like

    (gdb) info line *0x19c905
    Line 2855 of "53c7,8xx.c" starts at address 0x19c905 <intr_scsi+641>
       and ends at 0x19c913 <intr_scsi+655>.

Record this information.  Then, enter
    list <line number>

Ie,

    (gdb) list 2855
    2850    /*      printk("scsi%d : target %d lun %d unexpected disconnect\n",
    2851                host->host_no, cmd->cmd->target, cmd->cmd->lun); */
    2852            printk("host : 0x%x\n", (unsigned) host);
    2853            printk("host->host_no : %d\n", host->host_no);
    2854            printk("cmd : 0x%x\n", (unsigned) cmd);
    2855            printk("cmd->cmd : 0x%x\n", (unsigned) cmd->cmd);
    2856            printk("cmd->cmd->target : %d\n", cmd->cmd->target);
    2857            if (cmd) {
    2858                abnormal_finished(cmd, DID_ERROR << 16);
    2859            }
    2860            hostdata->dsp = hostdata->script + hostdata->E_schedule /
    2861                sizeof(long);
    2862            hostdata->dsp_changed = 1;
    2863        /* SCSI PARITY error */
    2864        }
    2865
    2866        if (sstat0_sist0 & SSTAT0_PAR) {
    2867            fatal = 1;
    2868            if (cmd && cmd->cmd) {
    2869                printk("scsi%d : target %d lun %d parity error.\n",

Obviously, quit will take you out of GDB.

Record this information too, as it will provide a context incase the
developers' kernels differ from yours.

Section 3 : Modules

This section gives specific details regarding the support for loadable
kernel modules and how it relates to SCSI.

Section 3.1 : General Information

Loadable modules are a means by which the user or system administrator
can load files into the kernel's memory in such a way that the kernel's
capabilities are expanded.  The most common usages of modules are for
drivers to support hardware, or to load filessytems.

There are several advantages of modules for SCSI.  One is that a
system administrator trying to maintain a large number of machines can
use a single kernel image for all of the machines, and then load
kernel modules to support hardware that is only present on some
machines.

It is also possible for someone trying to create a distribution to use
a script on the bootable floppy to query for which modules to be
loaded.  This saves memory that would otherwise be wasted on unused
drivers, and it would also reduce the possibility that a probe for a
non-existant card would screw up some other card on the system.

Modules also work out nicely on laptops, which tend to have less
memory than desktop machines, and people tend to want to keep the
kernel image as small as possible and load modules as required.  Also,
modules makes supporting PCMCIA SCSI cards on laptops somewhat easier,
since you can load and unload the driver as the card is
inserted/removed. [Note: currently the qlogic and 152x drivers support
PCMCIA].

Finally, there is the advantage that kernel developers can more easily
debug and test their drivers, since testing a new driver does not
require rebooting the machine (provided of course that the machine has
not completely crashed as a result of some bug in the driver).

Although modules are very nice, there is one limitation.  If your root
disk partition is on a scsi device, you will not be able to use
modularized versions of scsi code required to access the disk.  This
is because the system must be able to mount the root partition before
it can load any modules from disk.  There are people thinking about
ways of fixing the loader and the kernel so that the kernel can
self-load modules prior to attempting to mount the root filesystem,
so at some point in the future this limitation may be lifted.

Section 3.2 : Module support in the 1.2.N kernel.

In the 1.2.N series of kernels, there is partial support for SCSI
kernel modules.  While none of the high level drivers (such as disk,
tape, etc) can be used as modules, most of the low level drivers
(i.e. 1542, 1522) can be loaded and unloaded as required.  Each time
you load a low-level driver, the driver first searches for cards that
can be driven.  Next, the bus is scanned for each card that is found,
and then the internal data structures are set up so as to make it
possible to actually use the devices attached to the cards that the
driver is managing.

    When you are through with a low-level driver, you can unload
it.  You should keep in mind that usage counts are maintained based upon
mounted filesystems, open files, etc, so that if you are still using a
device that the driver is managing, the rmmod utillity will tell you that
the device is still busy and refuse to unload the driver.  When the driver
is unloaded, all of the associated data structures are also freed so that
the system state should be back to where it was before the module was loaded.
This means that the driver could be reloaded at a later time if required.

Section 3.3 : Module support in the 1.3.N kernel.

In the 1.3 series of kernels, the scsi code is completely modularized.
This means that you can start with a kernel that has no scsi support
whatsoever, and start loading modules and you will eventually end up
with complete support.

If you wish, you can compile some parts of the SCSI code into the kernel
and then load other parts later - it is all up to you how much gets loaded
at runtime and how much is linked directly into the kernel.

If you are starting with a kernel that has no support whatsoever for
SCSI, then the first thing you will need to do is to load the scsi
core into the kernel - this is in a module called "scsi_mod".  You
will not be able to load any other scsi modules until you have this
loaded into kernel memory.  Since this does not contain any low-level
drivers, the act of loading this module will not scan any busses, nor
will it activate any drivers for scsi disks, tapes, etc.  If you answered
'Y' to the CONFIG_SCSI question when you built your kernel, you will not
need to load this module.

At this point you can add modules in more or less any order to achieve
the desired functionality.  Usage counts are interlocks are used to
prevent unloading of any component which might still be in use, and
you will get a message from rmmod if a module is still busy.

The high level drivers are in modules named "sd_mod", "sr_mod", "st",
and "sg", for disk, cdrom, tape, and scsi generics support
respectively.  When you load a high level driver, the device list for
all attached hosts is examined for devices which the high level driver
can drive, and these are automatically activated.

The use of modules with low level drivers were described in the
Section 3.2.  When a low-level driver is loaded, the bus is scanned,
and each device is examined by each of the high level drivers to see
if they recognize it as something that they can drive - anything
recognized is automatically attached and activated.

Section 4 : Hosts

This section gives specific information about the various host adapters that
are supported in some way or another under linux.

Section 4.1 : Supported and Unsupported Hardware
Drivers in the distribution kernel :

Adaptec 152x, Adaptec 154x (DTC 329x boards usually work, but are unsupported),
Adaptec 174x, Adaptec 274x/284x (294x support requires a newer version of the
driver), BusLogic MultiMaster Host Adapters, EATA-DMA protocol compilant boards
(all DPT PMXXXXX/XX and SKXXXXX/XX except the PM2001, some boards from NEC and
ATT), Future Domain 850, 885, 950, and other boards in that series (but not the
840, 841, 880, and 881 boards unless you make the appropriate patch), Future
Domain 16x0 with TMC-1800, TMC-18C30, or TMC-18C50 chips, NCR53c8xx,PAS16 SCSI
ports, Seagate ST0x, Trantor T128/T130/T228 boards, Ultrastor 14F, 24F, and
34F, and Western Digital 7000.

MCA :

MCA boards which are compatable with a supported board (ie,
Adaptec 1640 and BusLogic 640) will work.

Alpha drivers :

Many ALPHA drivers are available at
   ftp://tsx-11.mit.edu/pub/linux/ALPHA/scsi

Drivers which will work with modifications

eata_dma:
   DPT PM2001

NCR53c8x0/7x0:

    A NCR53c8xx driver has been developed, but currently will not work
    with NCR53c700, NCR53c700-66, NCR53c710, and NCR53c720 chips.  A list
    of changes needed to make each of these chips work follows, as well
    as a summary of the complexity.

    NCR53c720 (trivial) - detection changes, initializaion changes, change
        fixup code to translate '810 register addresses to
    '7xx mapping.

    NCR53c710 (trivial) - detection changes, initialization changes,
    of assembler, change fixup code to translate '810 register
    addresses to '7xx mapping, change interrupt handlers to treat
    IID interrupt from INTFLY instruction to emulate it.

    NCR53c700, NCR53c700-66 (very messy) - detection changes,
        initialization changes, modification of NCR code to not use DSA,
    modification of Linux code to handle context switches.

SCSI hosts that will not work :

All parallel->SCSI adapters, Rancho SCSI boards, and Grass Roots SCSI
boards.  BusLogic FlashPoint boards, such as the BT-930/932/950, are
currently unsupported.

SCSI hosts that will NEVER work :

Non Adaptec compatable, non NCR53c8xx DTC boards (including the 3270 and 3280).

CMD SCSI boards.

Aquiring programming information requires a non-disclosure agreement
with DTC/CMD.  This means that it would be impossible to distribute a
Linux driver if one were written, since complying with the NDA would
mean distributing no source, in violation of the GPL, and complying
with the GPL would mean distributing source, in violation of the NDA.

If you want to run Linux on some other unsupported piece of hardware, your
options are to either write a driver yourself (Eric Youngdale and I are
usually willing to answer technical questions concerning the Linux
SCSI drivers) or to commision a driver (Normal consulting rates
mean that this will not be a viable option for personal use).

Section 4.1.1 : Multiple host adapters

With some host adapters (see Section 9.7 : Buyers' Guide :
Feature Comparison), you can use multiple host adapters of the
same type in the same system.  With multiple adapters of the
same type in the same system, generally the one at the lowest
address will be scsi0, the one at the next address scsi1, etc.

In all cases, it is possible to use multiple host adapters of
different types, provided that none of their addresses conflict.
SCSI controllers are scanned in the order specified in the
builtin_scsi_hosts[] array in drivers/scsi/hosts.c, with
the order currently being

    BusLogic, Ultrastor 14/34F, Ultrastor 14F,, Adaptec 151x/152x,
    Adaptec 154x, Adaptec 174x, AIC7XXX, AM53C974, Future Domain 16x0,
    Allways IN2000, Generic NCR5380, QLOGIC, PAS16, Seagate,
    Trantor T128/T130, NCR53c8xx, EATA-DMA, WD7000, debugging driver.

In most cases (ie, you aren't trying to use both BusLogic and Adaptec drivers),
this can be changed to suit your needs (ie, keeping the same devices when new
SCSI devices are added to the system on a new controller) by moving the
individual entries.

Section 4.2 : Common Problems
Section 4.2.1 : SCSI timeouts
    Make sure interrupts are enabled correctly, and there are no
    IRQ, DMA, or address conflicts with other boards.

Section 4.2.2 : Failure of autoprobe routines on boards that rely on
    BIOS for autoprobe.

    If your SCSI adapter is one of the following :

        Adaptec 152x, Adaptec 151x, Adaptec AIC-6260,
        Adaptec AIC-6360, Future Domain 1680, Future Domain TMC-950,
        Future Domain TMC-8xx, Trantor T128, Trantor T128F,
        Trantor T228F, Seagate ST01, Seagate ST02, or a
        Western Digital 7000

    and it is not detected on bootup, ie you get a

        scsi : 0 hosts

    message or a

        scsi%d : type

    message is not printed for each supported SCSI adapter installed
    in the system, you may have a problem with the autoprobe routine
    not knowing about your board.

    Autodetection will fail for drivers using the BIOS for autodetection
    if the BIOS is disabled.  Double check that your BIOS is enabled,
    and not conflicting with any other peripherial BIOSes.

    Autodetection will also fail if the board's "signature" and/or
    BIOS address don't match known ones.

    If the BIOS is installed, please use DOS and DEBUG to
    find a signature that will detect your board -

    Ie, if your board lives at 0xc8000, under DOS do

    debug
    d c800:0
    q

    and send a message to the SCSI channel of the mailing list with
    the ASCII message, with the length and offset from the base
    address (ie, 0xc8000).  Note that the EXACT text is required,
    and you should provide both the hex and ASCII portions of
    the text.

    If no BIOS is installed, and you are using an Adaptec 152x,
    Trantor T128, or Seagate driver, you can use command line
    or compile time overrides to force detection.

    Please consult the appropriate subsection for your SCSI board
    as well as Section 1.1 :


Section 4.2.3 : Failure of boards using memory mapped I/O

    (This include the Trantor T128 and Seagate boards, but not the
    Adaptec, Generic NCR5380, PAS16, and Ultrastor drivers)

    This is often caused when the memory mapped I/O ports
    are incorrectly cached.  You should have the board's
    address space marked as uncachable in the XCMOS settings.

    If this is not possible, you will have to disable cache
    entirely.

        If you have manually specified the address of the board,
        remember that Linux needs the actual address of the board,
        and not the 16 byte segment the documentation may refer to.

        Ie, 0xc8000 would be correct, 0xc800 would not work
        and could cause memory corruption.

Section 4.2.4 : "kernel panic : cannot mount root device" when booting
    an ALPHA driver boot floppy

    You'll need to edit the binary image of the kernel (before
    or after writing it out to disk), and modify a few two byte
    fields (little endian) to gurantee that it will work on your
    system.

    1.  default swap device at offset 502, this should be set to 0x00 0x00

    2.  ram disk size at offset 504, this should be set to the size
        of the boot floppy in K - ie, 5.25" = 1200, 3.5" = 1440.

        This means the bytes are

        3.5" : 0xA0 0x05
        5.25" : 0xB0  0x04

    3.  root device offset at 508, this should be 0x00 0x00, ie the boot
        device.

    dd or rawrite the file to a disk.  Insert the disk in the
    first floppy drive, wait until it prompts you to insert
    the root disk, and insert the root floppy from your
    distribution.


Section 4.2.5 : Installing a device driver not included with the distribution
    kernel

    You need to start with the version of the kernel used by the
    driver author.  This revision may be alluded to in the documentation
    included with the driver.

    Various recent kernel revisions can be found at
        nic.funet.fi:/pub/OS/Linux/PEOPLE/Linus

    as linux-version.tar.gz

    They are also mirrored at tsx-11.mit.edu and various other sites.

    cd to /usr/src.

    Remove your old Linux sources, if you want to keep a backup copy
    of them

    mv linux linux-old

    Untar the archive

    gunzip < linux-0.99.12.tar.gz | tar xvfp -

    Apply the patches.  The patches will be relative to some directory
    in the filesystem.  By examining the output file lines in the patch
    file (grep for ^---), you can tell where this is - ie patches with
    these lines

    --- ./kernel/blk_drv/scsi/Makefile

    --- ./config.in Wed Sep  1 16:19:33 1993


    would have the files relative to /usr/src/linux.

    Untar the driver sources at an appropriate place - you
    can type

    tar tfv patches.tar

    to get a listing, and move files as necessary (The SCSI driver files
    should live in /usr/src/linux/kernel/drivers/scsi)

    Either cd to the directory they are relative to and type

    patch -p0 < patch_file

    or tell patch to strip off leading path components.  Ie,
    if the files started with

    --- linux-new/kernel/blk_drv/scsi/Makefile

    and you wanted to apply them while in /usr/src/linux, you
    could cd to /usr/src/linux and type

    patch -p1 <  patches

    to strip off the "linux-new" component.

    After you have applied the patches, look for any patch rejects,
    which will be the name of the rejected file with a # suffix appended.

    find /usr/src/linux/ -name "*#" -print

    If any of these exist, look at them.  In some cases, the
    differences will be in RCS identifiers and will be harmless,
    in other cases, you'll have to manually apply important
    parts.  Documentation on diff files and patch is beyond the
    scope of this document.

    See also Section 1.8 : Configuring and building the kernel

Section 4.2.6 :  Installing a driver that has no patches

    In some cases, a driver author may not offer patches with
    the .c and .h files which comprise his driver, or the patches
    may be against an older revision of the kernel and not go
    in cleanly.

    1.  Copy the .c and .h files into /usr/src/linux/drivers/scsi

    2.  Add the configuration option

        Edit /usr/src/linux/config.in, and add a line in the

            *
            * SCSI low-level drivers
            *

        section, add a boolean configuration variable for your
        driver.  Ie,

        bool 'Allways IN2000 SCSI support' CONFIG_SCSI_IN2000 y

    3.  Add the makefile entries

        Edit /usr/src/linux/drivers/scsi/Makefile, and add
        an entry like

        ifdef CONFIG_SCSI_IN2000
        SCSI_OBS := $(SCSI_OBJS) in2000.o
        SCSI_SRCS := $(SCSI_SRCS) in2000.c
        endif

        before the

        scsi.a: $(SCSI_OBJS)

        line in the makefile, where the .c file is the .c
        file you copied in, and the .o file is the basename
        of the .c file with a .o suffixed.

    4.  Add the entry points

        Edit /usr/src/linux/drivers/scsi/hosts.c, and
        add a #inlclude for the header file, conditional
        on the CONFIG_SCSI preprocessor define you
        added to the configuration file.  Ie, after

        #ifdef CONFIG_SCSI_GENERIC_NCR5380
        #include "g_NCR5380.h"
        #endif

        you might add

        #ifdef CONFIG_SCSI_IN2000
        #include "in2000.h"
        #endif

        You will also need to add the Scsi_Host_Template
        entry into the scsi_hosts[] array.  Take a look
        into the .h file, and you should find a #define that
        looks something like this :

        #define IN2000 {"Always IN2000", in2000_detect, \
                in2000_info, in2000_command,    \
                in2000_queuecommand,            \
                in2000_abort,                   \
                in2000_reset,                   \
                NULL,                           \
                in2000_biosparam,               \
                1, 7, IN2000_SG, 1, 0, 0}

        the name of the preprocessor define, and add
        it into the scsi_hosts[] array, conditional on
        definition of the preprocessor symbol you used
        in the configuration file.

        Ie, after

        #ifdef CONFIG_SCSI_GENERIC_NCR5380
                GENERIC_NCR5380,
        #endif

        you might add

        #ifdef CONFIG_SCSI_IN2000
            IN2000,
        #endif

    See also Section 1.8 : Configuring and building the kernel

Section 4.2.7 : Failure of a PCI board in a Compaq System

    A number of Compaq systems map the 32-bit BIOS extensions used
    to probe for PCI devices into memory which is inaccessable to
    the Linux kernel due to the memory layout.  If Linux is
    unable to detect a supported PCI SCSI board, and the
    kernel tells you something like

    pcibios_init: entry in high memory, unable to access

    Grab

        ftp://ftp.compaq.com/pub/softpaq/Software-Solutions/sp0921.zip

    which is a self-extracting archive of a program which will
    relocate the BIOS32 code.

Section 4.2.8 : A SCSI system with PCI boards hangs after the
    %d Hosts message

    Some PCI systems have broken BIOSes which disable interrupts
    and fail to renable them before returning control to the
    caller.  The following patch fixes this

--- bios32.c.orig    Mon Nov 13 22:35:31 1995
+++ bios32.c    Thu Jan 18 00:15:09 1996
@@ -56,6 +56,7 @@
 #include <linux/pci.h>

 #include <asm/segment.h>
+#include <asm/system.h>

 #define PCIBIOS_PCI_FUNCTION_ID     0xb1XX
 #define PCIBIOS_PCI_BIOS_PRESENT     0xb101
@@ -125,7 +126,9 @@
     unsigned long address;        /* %ebx */
     unsigned long length;        /* %ecx */
     unsigned long entry;        /* %edx */
+    unsigned long flags;

+    save_flags(flags);
     __asm__("lcall (%%edi)"
         : "=a" (return_code),
           "=b" (address),
@@ -134,6 +137,7 @@
         : "0" (service),
           "1" (0),
           "D" (&bios32_indirect));
+    restore_flags(flags);

     switch (return_code) {
         case 0:
@@ -161,11 +165,13 @@
     unsigned char present_status;
     unsigned char major_revision;
     unsigned char minor_revision;
+    unsigned long flags;
     int pack;

     if ((pcibios_entry = bios32_service(PCI_SERVICE))) {
         pci_indirect.address = pcibios_entry;

+        save_flags(flags);
         __asm__("lcall (%%edi)\n\t"
             "jc 1f\n\t"
             "xor %%ah, %%ah\n"
@@ -176,6 +182,7 @@
             : "1" (PCIBIOS_PCI_BIOS_PRESENT),
               "D" (&pci_indirect)
             : "bx", "cx");
+        restore_flags(flags);

         present_status = (pack >> 16) & 0xff;
         major_revision = (pack >> 8) & 0xff;
@@ -210,7 +217,9 @@
 {
     unsigned long bx;
     unsigned long ret;
+    unsigned long flags;

+    save_flags(flags);
     __asm__ ("lcall (%%edi)\n\t"
         "jc 1f\n\t"
         "xor %%ah, %%ah\n"
@@ -221,6 +230,7 @@
           "c" (class_code),
           "S" ((int) index),
           "D" (&pci_indirect));
+    restore_flags(flags);
     *bus = (bx >> 8) & 0xff;
     *device_fn = bx & 0xff;
     return (int) (ret & 0xff00) >> 8;
@@ -232,7 +242,9 @@
 {
     unsigned short bx;
     unsigned short ret;
+    unsigned long flags;

+    save_flags(flags);
     __asm__("lcall (%%edi)\n\t"
         "jc 1f\n\t"
         "xor %%ah, %%ah\n"
@@ -244,6 +256,7 @@
           "d" (vendor),
           "S" ((int) index),
           "D" (&pci_indirect));
+    restore_flags(flags);
     *bus = (bx >> 8) & 0xff;
     *device_fn = bx & 0xff;
     return (int) (ret & 0xff00) >> 8;
@@ -254,7 +267,9 @@
 {
     unsigned long ret;
     unsigned long bx = (bus << 8) | device_fn;
+    unsigned long flags;

+    save_flags (flags);
     __asm__("lcall (%%esi)\n\t"
         "jc 1f\n\t"
         "xor %%ah, %%ah\n"
@@ -273,7 +288,9 @@
 {
     unsigned long ret;
     unsigned long bx = (bus << 8) | device_fn;
+    unsigned long flags;

+    save_flags(flags);
     __asm__("lcall (%%esi)\n\t"
         "jc 1f\n\t"
         "xor %%ah, %%ah\n"
@@ -292,7 +309,9 @@
 {
     unsigned long ret;
     unsigned long bx = (bus << 8) | device_fn;
+    unsigned long flags;

+    save_flags(flags);
     __asm__("lcall (%%esi)\n\t"
         "jc 1f\n\t"
         "xor %%ah, %%ah\n"
@@ -303,6 +322,7 @@
           "b" (bx),
           "D" ((long) where),
           "S" (&pci_indirect));
+    restore_flags(flags);
     return (int) (ret & 0xff00) >> 8;
 }

@@ -311,7 +331,9 @@
 {
     unsigned long ret;
     unsigned long bx = (bus << 8) | device_fn;
+    unsigned long flags;

+    save_flags(flags);
     __asm__("lcall (%%esi)\n\t"
         "jc 1f\n\t"
         "xor %%ah, %%ah\n"
@@ -322,6 +344,7 @@
           "b" (bx),
           "D" ((long) where),
           "S" (&pci_indirect));
+    restore_flags(flags);
     return (int) (ret & 0xff00) >> 8;
 }

@@ -330,7 +353,9 @@
 {
     unsigned long ret;
     unsigned long bx = (bus << 8) | device_fn;
+    unsigned long flags;

+    save_flags(flags);
     __asm__("lcall (%%esi)\n\t"
         "jc 1f\n\t"
         "xor %%ah, %%ah\n"
@@ -341,6 +366,7 @@
           "b" (bx),
           "D" ((long) where),
           "S" (&pci_indirect));
+    restore_flags(flags);
     return (int) (ret & 0xff00) >> 8;
 }

@@ -349,7 +375,9 @@
 {
     unsigned long ret;
     unsigned long bx = (bus << 8) | device_fn;
+    unsigned long flags;

+    save_flags(flags);
     __asm__("lcall (%%esi)\n\t"
         "jc 1f\n\t"
         "xor %%ah, %%ah\n"
@@ -360,6 +388,7 @@
           "b" (bx),
           "D" ((long) where),
           "S" (&pci_indirect));
+    restore_flags(flags);
     return (int) (ret & 0xff00) >> 8;
 }

Section 4.3 : Adaptec 152x, 151x, 1505, 282x, Sound Blaster 16 SCSI, SCSI Pro,
    Gigabyte, and other AIC 6260/6360 based products (Standard)
Supported Configurations :
BIOS addresses : 0xd8000, 0xdc000, 0xd0000, 0xd4000, 0xc8000, 0xcc000, 0xe0000,
    0xe4000.
Ports : 0x140, 0x340
IRQs : 9, 10, 11, 12
DMA is not used
IO : port mapped

Autoprobe :

    Works with many boards with an installed BIOS.  All
    other boards, including the Adaptec 1510, and Sound Blaster16 SCSI
    must use a kernel command line or compile time override.

Autoprobe Override :
Compile time :
Define PORTBASE, IRQ, SCSI_ID, RECONNECT, PARITY as appropriate, see Defines

kernel command line : aha152x=<PORTBASE>[,<IRQ>[,<SCSI-ID>[,<RECONNECT>[,<PARITY>]]]]

SCSI-ID is the SCSI ID of the HOST adapter, not of any devices you have installed
on it.  Usually, this should be 7.

To force detection at 0x340, IRQ 11, at SCSI-ID 7, allowing
disconnect/reconnect, you would use the following command line
option :

aha152x=0x340,11,7,1

Antiquity Problems, fix by upgrading :
1.  The driver fails with VLB boards.  There was a timing problem
    in kernels older than revision 1.0.5.

Defines :
AUTOCONF      : use configuration the controller reports (only 152x)
IRQ           : override interrupt channel (9,10,11 or 12) (default 11)
SCSI_ID       : override SCSI ID of AIC-6260 (0-7) (default 7)
RECONNECT     : override target disconnect/reselect (set to non-zero to
        allow, zero to disable)
DONT_SNARF     : Don't register ports (pl12 and below)
SKIP_BIOSTEST  : Don't test for BIOS signature (AHA-1510 or disabled BIOS)
PORTBASE       : Force port base. Don't try to probe

Section 4.4 : Adaptec 154x, AMI FastDisk VLB, DTC 329x (Standard)
Supported Configurations :
Ports : 0x330 and 0x334
IRQs : 9, 10, 11, 12, 14, 15
DMA channels : 5, 6, 7
IO : port mapped, bus master

Autoprobe : will detect boards at 0x330 and 0x334 only.

Autoprobe override :
   aha1542=<PORTBASE>[,<BUSON>,<BUSOFF>[,<DMASPEED>]]

Note: No-suffix boards, and early 'A' suffix boards do not support
    scatter/gather, and thus don't work.  However, they can be made to
    work for some definition of the word works if AHA1542_SCATTER is
    changed to 0 in drivers/scsi/aha1542.h.

Note: BusLogic makes a series of boards that are software compatible with
    the Adaptec 1542, and these come in ISA, VLB, EISA, and PCI flavors.

Antiquity Problems, fix by upgrading :

1.  Linux kernel revisions prior to .99.10 don't support the 'C'
    revision.

2.  Linux kernel revisions prior to .99.14k don't support the 'C'
    revision options for

    - BIOS support for the extended mapping for disks > 1G

    - BIOS support for > 2 drives

    - BIOS support for autoscanning the SCSI bus

3.  Linux kernel revisions prior to .99.15e don't support the 'C'
    with the BIOS support for > 2 drives turned on and the
    BIOS support for the extended mapping for disks > 1G turned off.

4.  Linux kernel revisions prior to .99.14u don't support the 'CF'
    revisions of the board.

5.  Linux kernel revisions prior to 1.0.5 have a race condition
    when multiple devices are accessed at the same time.

Common problems :

1.  There are unexpected errors with a 154xC or 154xCF board,

    Early examples of the 154xC boards have a high slew rate on
    one of the SCSI signals, which results in signal reflections
    when cables with the wrong impedance are used.

    Newer boards aren't much better, and also suffer from extreme
    cabling and termination sensitivity.

    See also Common Problems #2 and #3 and Section 1 : Common Problems,
    Subsection 1.1 : General Flakiness

2.  There are unexpected errors with a 154xC or 154x with
    both internal and external devices connected.

    This is probably a termination problem.  In order to
    use the software option to disable host adapter termination,
    you must turn switch 1 off.

    See also Common Problems #1 and #3 and Section 1 : Common Problems,
    Subsection 1.1 : General Flakiness

3.  The SCSI subsystem locks up completely.

    There are cases where the lockups seem to occur when multiple devices
    are in use at the same time.  In this case, you can try contacting
    the manufacturer of the devices and see if firmware upgrades are
    available which would correct the problem.  As a last resort, you
    can go into aha1542.h and change AHA1542_MAILBOX to 1.  This will
    effectively limit you to one outstanding command on the scsi bus at
    one time, and may help the situation.  If you have tape drives or
    slow cdrom drives on the bus, this might not be a practical solution.

    See also Common Problems #1 and #2 and
    Section 1.1 : Common Problems : General Flakiness
    Section 1.8 : Common Problems : SCSI Lockups

4.  An "Interrupt received, but no mail" message is printed on bootup
    and your SCSI devices are not detected.

    Disable the BIOS options to support the extended mapping for
    disks > 1G, support for > 2 drives, and for autoscanning the
    bus.  Or, upgrade to Linux .99.14k or newer.

5.  If infinite timeout errors occur on 'C' revision boards,  you may need
        to go into the Adaptec setup program and enable synchronous
    negotiation.

6.  Linux 1.2.x gives the message

    Unable to determine Adaptec DMA priority.  Disabling board.

    This is due to a conflict on some systems with the obsolete BusLogic
    driver.  Either rebuild your kernel without it, or give the
    BusLogic driver a command line option telling it to look
    somewhere other than where your controller is configured.  Ie,
    if you have an Adaptec board at port 0x334, and nothing at
    0x330, use a command line option like

    buslogic=0x330

8.  The system locks up with simultaneous access to multiple devices on
    a 1542C or 1540C and disconnection enabled

    Some Adaptec firmware revisions have bugs.  Upgrading to
    BIOS v2.11 purportedly fixes these problems.

Section 4.5 : Adaptec 174x
Supported Configurations :
Slots : 1-8
Ports : EISA board, not applicable
IRQs : 9, 10, 11, 12, 14, 15
DMA Channels : EISA board, not applicable
IO : port mapped, bus master

Autoprobe : works with all supported configurations

Autoprobe override : none

Note: This board has been discontinued by Adaptec.

Common Problems :
1. If the Adaptec 1740 driver prints the message
    "aha1740: Board detected, but EBCNTRL = %x, so disabled it."

    your board was disabled because it was not running in enhanced
        mode.  Boards running in standard 1542 mode are not supported.

Section 4.6 : Adaptec 274x, 284x (Standard) 294x (ALPHA)
    A newer version which also supports the Adaptec 294x boards
is available at

    ftp://ftp.ims.com/pub/Linux/aic7xxx

Supported Configurations
        274x            284x        294x
EISA Slots :     1-12            N/A        N/A
Ports :     N/A            ALL        ALL
IRQs :         ALL            ALL        ALL
DMA Channels :     N/A            ALL        N/A

IO : port mapped, bus master

Autoprobe Override :
kernel command line : aha274x=extended
    (to force extended mapping)

Notes:
1.  BIOS MUST be enabled
2.  The B channel on 2742AT boards is ignored.
3.  CONFIG_PCI must be set if you are using a PCI board.


Section 4.7 : Allways IN2000  (STANDARD)
Ports : 0x100, 0x110, 0x200, 0x220
IRQs : 10, 11, 14, 15
DMA is not used
IO : port mapped

Autoprobe : BIOS not required

Autoprobe override : none

Common Problems :

1.  There are known problems in systems with IDE drives and with
    swapping.


Section 4.8 : BusLogic MultiMaster Host Adapters

(this section Copyright 1995 by Leonard N. Zubkoff <[e-mail]>)
(see README.BusLogic for more complete BusLogic driver documentation)

          BusLogic MultiMaster SCSI Driver for Linux

               Version 1.2.2 for Linux 1.2.13
               Version 1.3.2 for Linux 1.3.88

         ftp://ftp.dandelion.com/BusLogic-1.2.2.tar.gz
         ftp://ftp.dandelion.com/BusLogic-1.3.2.tar.gz

                 16 April 1996

                   Leonard N. Zubkoff
                   Dandelion Digital
                   [e-mail]

BusLogic, Inc. designs and manufactures a variety of high performance SCSI host
adapters which share a common programming interface across a diverse collection
of bus architectures by virtue of their MultiMaster ASIC technology.  This
driver supports all present BusLogic MultiMaster Host Adapters, and should
support any future MultiMaster designs with little or no modification.  Host
adapters based on the new FlashPoint architecture are not supported by this
driver; consult the README.FlashPoint file for information about a program to
upgrade Linux users from the unsupported FlashPoint LT to the supported BT-948.

My primary goals in writing this completely new BusLogic driver for Linux are
to achieve the full performance that BusLogic SCSI Host Adapters and modern
SCSI peripherals are capable of, and to provide a highly robust driver that can
be depended upon for high performance mission critical applications.  All of
the major performance and error recovery features can be configured from the
Linux kernel command line, allowing individual installations to tune driver
performance and error recovery to their particular needs.

BusLogic has been an excellent company to work with and I highly recommend
their products to the Linux community.  In November 1995, I was offered the
opportunity to become a beta test site for their latest MultiMaster product,
the BT-948 PCI Ultra SCSI Host Adapter, and then again for the BT-958 PCI Wide
Ultra SCSI Host Adapter in January 1996.  This was mutually beneficial since
BusLogic received a degree and kind of testing that their own testing group
cannot readily achieve, and the Linux community has available high performance
host adapters that have been well tested with Linux even before being brought
to market.  This relationship has also given me the opportunity to interact
directly with their technical staff, to understand more about the internal
workings of their products, and in turn to educate them about the needs and
potential of the Linux community.  Their interest and support is greatly
appreciated.

Unlike some other vendors, if you contact BusLogic Technical Support with a
problem and are running Linux, they will not tell you that your use of their
products is unsupported.  Their latest product marketing literature even states
"BusLogic SCSI host adapters are compatible with all major operating systems
including: ... Linux ...".

BusLogic, Inc. is located at 4151 Burton Drive, Santa Clara, California, 95054,
USA and can be reached by Voice at 408/492-9090 or by FAX at 408/492-1542.
BusLogic maintains a World Wide Web site at http://www.buslogic.com, an
anonymous FTP site at ftp.buslogic.com, and a BBS at 408/492-1984.  BusLogic
Technical Support can be reached by electronic mail at [e-mail], by
Voice at 408/654-0760, or by FAX at 408/492-1542.  Contact information for
offices in Europe and Japan is available on the Web site.

                SUPPORTED HOST ADAPTERS

The following list comprises the supported BusLogic SCSI Host Adapters as of
the date of this document.  It is recommended that anyone purchasing a BusLogic
Host Adapter not in the following table contact the author beforehand to verify
that it is or will be supported.

"W" Series Host Adapters:

BT-948        PCI        Ultra Fast Single-ended SCSI-2
BT-958        PCI        Ultra Wide Single-ended SCSI-2
BT-958D        PCI        Ultra Wide Differential SCSI-2

"C" Series Host Adapters:

BT-946C        PCI        Fast Single-ended SCSI-2
BT-956C        PCI        Fast Wide Single-ended SCSI-2
BT-956CD    PCI        Fast Wide Differential SCSI-2
BT-445C        VLB        Fast Single-ended SCSI-2
BT-747C        EISA    Fast Single-ended SCSI-2
BT-757C        EISA    Fast Wide Single-ended SCSI-2
BT-757CD    EISA    Fast Wide Differential SCSI-2
BT-545C        ISA        Fast Single-ended SCSI-2
BT-540CF    ISA        Fast Single-ended SCSI-2

"S" Series Host Adapters:

BT-445S        VLB        Fast Single-ended SCSI-2
BT-747S        EISA    Fast Single-ended SCSI-2
BT-747D        EISA    Fast Differential SCSI-2
BT-757S        EISA    Fast Wide Single-ended SCSI-2
BT-757D        EISA    Fast Wide Differential SCSI-2
BT-545S        ISA        Fast Single-ended SCSI-2
BT-542D        ISA        Fast Differential SCSI-2
BT-742A        EISA    Single-ended SCSI-2 (742A revision H)
BT-542B        ISA        Single-ended SCSI-2 (542B revision H)

"A" Series Host Adapters:

BT-742A        EISA    Single-ended SCSI-2 (742A revisions A - G)
BT-542B        ISA        Single-ended SCSI-2 (542B revisions A - G)

AMI FastDisk Host Adapters that are true BusLogic clones are supported by this
driver.

              BT-948/958/958D INSTALLATION NOTES

The BT-948/958/958D PCI Ultra SCSI Host Adapters have some features which may
require attention in some circumstances when installing Linux.

o PCI I/O Port Assignments

  When configured to factory default settings, the BT-948/958/958D will only
  recognize the PCI I/O port assignments made by the motherboard's PCI BIOS.
  The BT-948/958/958D will not respond to any of the ISA compatible I/O ports
  that previous BusLogic SCSI Host Adapters respond to.  This driver supports
  the PCI I/O port assignments, so this is the preferred configuration.
  However, if the obsolete BusLogic driver must be used for any reason, such as
  a Linux distribution that does not yet use this driver in its boot kernel,
  BusLogic has provided an AutoSCSI configuration option to enable a legacy ISA
  compatible I/O port.

  To enable this backward compatibility option, invoke the AutoSCSI utility via
  Ctrl-B at system startup and select "Adapter Configuration", "View/Modify
  Configuration", and then change the "ISA Compatible Port" setting from
  "Disable" to "Primary" or "Alternate".  Once this driver has been installed,
  the "ISA Compatible Port" option should be set back to "Disable" to avoid
  possible future I/O port conflicts.  The older BT-946C/956C/956CD also have
  this configuration option, but the factory default setting is "Primary".

o PCI Slot Scanning Order

  In systems with multiple BusLogic PCI Host Adapters, the order in which the
  PCI slots are scanned may appear reversed with the BT-948/958/958D as
  compared to the BT-946C/956C/956CD.  For booting from a SCSI disk to work
  correctly, it is necessary that the host adapter's BIOS and the kernel agree
  on which disk is the boot device, which requires that they recognize the PCI
  host adapters in the same order.  The motherboard's PCI BIOS provides a
  standard way of enumerating the PCI host adapters, which is used by the Linux
  kernel.  Some PCI BIOS implementations enumerate the PCI slots in order of
  increasing bus number and device number, while others do so in the opposite
  direction.

  Unfortunately, Microsoft decided that Windows 95 would always enumerate the
  PCI slots in order of increasing bus number and device number regardless of
  the PCI BIOS enumeration, and requires that their scheme be supported by the
  host adapter's BIOS to receive Windows 95 certification.  Therefore, the
  factory default settings of the BT-948/958/958D enumerate the host adapters
  by increasing bus number and device number.  To disable this feature, invoke
  the AutoSCSI utility via Ctrl-B at system startup and select "Adapter
  Configuration", "View/Modify Configuration", press Ctrl-F10, and then change
  the "Use Bus And Device # For PCI Scanning Seq." option to OFF.

  This driver will interrogate the setting of the PCI Scanning Sequence option
  so as to recognize the host adapters in the same order as they are enumerated
  by the host adapter's BIOS.

              BUSLOGIC ANNOUNCEMENTS MAILING LIST

The BusLogic Announcements Mailing List provides a forum for informing Linux
users of new driver releases and other announcements regarding Linux support
for BusLogic SCSI Host Adapters.  To join the mailing list, send a message to
"[e-mail]" with the line "subscribe" in the
message body.


Section 4.9 : BusLogic FlashPoint Host Adapters
(this section Copyright 1995 by Leonard N. Zubkoff <[e-mail]>)

There are no Linux drivers for the FlashPoint LT/DL/LW (BT-930/932/950)
available and it is not clear when or if there will be any.  The FlashPoint
boards have a different architecture from the MultiMaster boards and have no
onboard CPU, only a SCSI sequencer engine.  They are positioned as a desktop
workstation product, and are not particularly well suited for a high
performance multitasking operating system like Linux.

The MultiMaster BT-948/958 have an onboard CPU and the mailbox programming
interface allows for parallelism and pipelining between the host operating
system and the host adapter, whereas the FlashPoint boards require frequent
host CPU intervention.  As interrupt latencies rise in a loaded multitasking
system, the BT-948/958 should maintain excellent performance whereas the
FlashPoint's performance will likely drop quite rapidly.  Furthermore, the
firmware on the BT-948/958 contains the low level knowledge for proper
interaction with the SCSI bus, whereas with a sequencer engine the Linux driver
must contain some or all of this information, and it often takes quite a long
time to get all the kinks worked out.  Given the relatively small difference in
the street price of these products, the BT-948 or BT-958 is clearly the better
choice for Linux.

<begin quotation>

                 ANNOUNCEMENT
          BusLogic FlashPoint/BT-948 Upgrade Program
                1 February 1996

Ever since its introduction last October, the BusLogic FlashPoint LT has
been problematic for members of the Linux community, in that no Linux
drivers have been available for this new Ultra SCSI product.  Despite it's
officially being positioned as a desktop workstation product, and not being
particularly well suited for a high performance multitasking operating
system like Linux, the FlashPoint LT has been touted by computer system
vendors as the latest thing, and has been sold even on many of their high
end systems, to the exclusion of the older MultiMaster products.  This has
caused grief for many people who inadvertently purchased a system expecting
that all BusLogic SCSI Host Adapters were supported by Linux, only to
discover that the FlashPoint was not supported and would not be for quite
some time, if ever.

After this problem was identified, BusLogic contacted its major OEM
customers to make sure the BT-946C/956C MultiMaster cards would still be
made available, and that Linux users who mistakenly ordered systems with
the FlashPoint would be able to upgrade to the BT-946C.  While this helped
many purchasers of new systems, it was only a partial solution to the
overall problem of FlashPoint support for Linux users.  It did nothing to
assist the people who initially purchased a FlashPoint for a supported
operating system and then later decided to run Linux, or those who had
ended up with a FlashPoint LT, believing it was supported, and were unable
to return it.

In the middle of December, I asked to meet with BusLogic's senior
management to discuss the issues related to Linux and free software support
for the FlashPoint.  Rumors of varying accuracy had been circulating
publicly about BusLogic's attitude toward the Linux community, and I felt
it was best that these issues be addressed directly.  I sent an email
message after 11pm one evening, and the meeting took place the next
afternoon.  Unfortunately, corporate wheels sometimes grind slowly,
especially when a company is being acquired, and so it's taken until now
before the details were completely determined and a public statement could
be made.

BusLogic is not prepared at this time to release the information necessary
for third parties to write drivers for the FlashPoint.  The only existing
FlashPoint drivers have been written directly by BusLogic Engineering, and
there is no FlashPoint documentation sufficiently detailed to allow outside
developers to write a driver without substantial assistance.  While there
are people at BusLogic who would rather not release the details of the
FlashPoint architecture at all, that debate has not yet been settled either
way.  In any event, even if documentation were available today it would
take quite a while for a usable driver to be written, especially since I'm
not convinced that the effort required would be worthwhile.

However, BusLogic does remain committed to providing a high performance
SCSI solution for the Linux community, and does not want to see anyone left
unable to run Linux because they have a Flashpoint LT.  Therefore, BusLogic
has put in place a direct upgrade program to allow any Linux user worldwide
to trade in their FlashPoint LT for the new BT-948 MultiMaster PCI Ultra
SCSI Host Adapter.  The BT-948 is the Ultra SCSI successor to the BT-946C
and has all the best features of both the BT-946C and FlashPoint LT,
including smart termination and a flash PROM for easy firmware updates, and
is of course compatible with the present Linux driver.  The price for this
upgrade has been set at US $45, and the upgrade program will be
administered through BusLogic Technical Support, which can be reached by
electronic mail at [e-mail], by Voice at [phone], or by
FAX at [phone].

I was a beta test site for the BT-948 and versions 1.2.1 and 1.3.1 of my
BusLogic driver already include latent support for the BT-948.  Additional
cosmetic support for the Ultra SCSI MultiMaster cards will be added in a
subsequent release.  As a result of this cooperative testing process,
several firmware bugs were found and corrected (make sure you have firmware
version 5.05R or later).  My heavily loaded Linux test system provided an
ideal environment for testing error recovery processes that are much more
rarely exercised in production systems, but are crucial to overall system
stability.  It was especially convenient being able to work directly with
their firmware engineer in demonstrating the problems under control of the
firmware debugging environment; things sure have come a long way since the
last time I worked on firmware for an embedded system.  I am presently
working on some performance testing and expect to have some data to report
in the not too distant future.

BusLogic asked me to send this announcement since a large percentage of the
questions regarding support for the FlashPoint have either been sent to me
directly via email, or have appeared in the Linux newsgroups in which I
participate.  To summarize, BusLogic is offering Linux users an upgrade
from the unsupported FlashPoint LT (BT-930) to the supported BT-948 for US
$45.  Contact BusLogic Technical Support at [e-mail] or +1 408
654-0760 to take advantage of their offer.

        Leonard N. Zubkoff
        [e-mail]

<end quotation>


Section 4.10 : EATA: DPT Smartcache, Smartcache Plus, Smartcache III (Standard)
Supported boards: all, that support the EATA-DMA protocol (no PM2001).
           DPT Smartcache: PM2011  PM2012A
                                   PM2012B
           Smartcache III: PM2021  PM2022  PM2024
                                   PM2122  PM2124
                                   PM2322
           SmartRAID     : PM3021  PM3222  PM3224
       many of those boards are also available as SKXXXX versions,
           which are supported as well.

Supported Configurations :
Slots        : ALL
Ports        : ALL
IRQs         : ALL level & edge triggered
DMA Channels : ISA ALL, EISA/PCI not applicable
IO           : port mapped, bus master
SCSI Channels: ALL
Autoprobe    : works with all supported configurations
Autoprobe Override :
 Compile time : diskgeometry in eata_dma.h for unusual disk geometries
               which came from the usage of the old DPTFMT utility.
The latest version of the EATA-DMA driver and a Slackware bootdisk should
be available on:
  ftp.uni-mainz.de:/pub/Linux/arch/i386/system/EATA/

Common Problems :
1.  The IDE driver detects the ST-506 interface of the EATA board.
1.1     This will look like similar to one of the following 2 examples:

    hd.c: ST-506 interface disk with more than 16 heads detected,
      probably due to non-standard sector translation.  Giving up.
      (disk %d: cyl=%d, sect=63, head=64)

        hdc: probing with STATUS instead of ALTSTATUS
        hdc: MP0242 A, 0MB w/128KB Cache, CHS=0/0/0
     hdc: cannot handle disk with 0 physical heads
     hdd: probing with STATUS instead of ALTSTATUS
     hdd: MP0242 A, 0MB w/128KB Cache, CHS=0/0/0
     hdd: cannot handle disk with 0 physical heads

        If the IDE driver gets into trouble because of this, ie. you can't
    access your (real) IDE hardware, change the IO Port and/or the IRQ of
    the EATA board.
1.2     If the IDE driver finds hardware it can handle ie. harddisks with
        a capacity <=504MB, it will allocate the IO Port and IRQ, so that
        the eata driver can't utilize them. In this case also change IO Port
        and IRQ (!= 14,15).


2. Some old SK2011 boards have a broken firmware. Please contact DPT's
        customer support for an update.

Notes:
1.  CONFIG_PCI must be set if you are using a PCI board.

Section 4.11 : Future Domain 16x0 with TMC-1800, TMC-18C30, TMC-18C50,
    or TMC-36C70 chip
Supported Configurations :
BIOSs :  2.0, 3.0, 3.2, 3.4, 3.5
BIOS Addresses :    0xc8000, 0xca000, 0xce000, 0xde000
Ports : 0x140, 0x150, 0x160, 0x170
IRQs : 3, 5, 10, 11, 12, 14, 15
DMA is not used
IO : port mapped

Autoprobe : works with all supported configurations, requires
    installed BIOS

Autoprobe Override : none

Antiquity Problems, fix by upgrading :

1.  Old versions do not support the TMC-18C50 chip, and will fail with
    newer boards.

2.  Old versions will not have the most current BIOS signatures for
    autodetection.

3.  Versions prior to the one included in Linux 1.0.9 and 1.1.6
    don't support the new SCSI chip or 3.4 BIOS.

Notes :
    The Future Domain BIOS often scans for SCSI-devices from highest
    ID to 0, in reverse order of other SCSI BIOSes.  sda will be the last
    "drive letter" (ie, D: rather than C:).  You may also need to use a
    a disktab override for LILO.

Section 4.12 : Generic NCR5380 / T130B
Supported and Unsupported Configurations :
Ports : all
IRQs : all
DMA channels - DMA is not used
IO : port mapped

Autoprobe : none

Autoprobe Override :
Compile time : Define GENERIC_NCR5380_OVERRIDE to be an array of tupples
with port, irq, dma, board type - ie
#define GENERIC_NCR5380_OVERRIDE {{0x330, 5, DMA_NONE, BOARD_NCR5380}}

for a NCR5380 board at port 330, IRQ 5.

#define GENERIC_NCR5380_OVERRIDE {{0x350, 5, DMA_NONE, BOARD_NCR53C400}}

for a T130B at port 0x350.

Older versions of the code eliminate the BOARD_* entry.

The symbolic IRQs IRQ_NONE and IRQ_AUTO may be used.

kernel command line : ncr5380=port,irq
              ncr5380=port,irq,dma
              ncr53c400=port,irq

255 may be used for no irq, 254 for irq autoprobe.

Common Problems :

1. Using the T130B board with the old (pre public release 6) generic
    NCR5380 driver which doesn't support the ncr53c400 command
    line option.

    The NCR5380 compatable registers are offset eight from
    the base address.  So, if your address is 0x350, use

    ncr5380=0x358,254

    on the kernel command line.

Antiquity problems, fix by upgrading :
1.  The kernel locks up during disk access with T130B or other
    NCR53c400 boards

    Pre-public release 6 versions of the Generic NCR5380
    driver didn't support interrupts on these boards.
    Upgrade.


Notes : the generic driver doesn't support DMA yet, and pseudo-DMA
    isn't supported in the generic driver.

Section 4.13 : NCR53c8xx (Standard)

Supported and Unsupported Configurations :
Base addresses : ALL
IRQs : ALL
DMA channels : PCI, not applicable
IO : port mapped, busmastering

Autoprobe : requires PCI BIOS, uses PCI BIOS routines to
    search for devices and read configuration space

The driver uses the pre-programmed values in some registers for
initialization, so a BIOS must be installed.

Antiquity Problems, fix by upgrading :

1.  Older versions of Linux had a problem with swapping
    See Section 5.2.7 : Disks :  System Hangs When Swapping

2.  Older versions of Linux didn't recognize '815 and '825
    boards.

3.  Distribution kernels include release 4 or 5 of the driver, which does
    not support useful things like disconnect/reconnect (the most noticeable
    effect of this being attempts to retension/rewind/file space a tape
    lock you out of all SCSI devices), multiple host adapters, and
    BIOSless operation.

    The latest release of the driver is available at

    ftp://tsx-11.mit.edu/pub/linux/ALPHA/scsi/ncr53c810

    Currently, this is a 1.2.10 and newer patch, although the next
    release will be 1.3.x exclusively.  These patches are NOT
    entirely clean due to some ELF and other patches which were
    in the baseline revision of my source tree, and if you
    can't manually correct the (four) problems you should get,
    you shouldn't use them.  Note that only the newest patch is
    needed; these are not incremental.

    If you wish to run the newer NCR driver with a 1.3.x kernel
    before then, Harald Evensen <[e-mail]> has
    adapted the patches for 1.3.x

    ftp://ftp.pvv.unit.no/pub/Linux/ALPHA/ncr

    These patches should be clean.

    Please see all of the READMEs in these directories.  You should
    also join the NCR mailing list if you are interested in running
    the ALPHA code, since interim bug fixes and announcements of the
    next release are posted to this list.

    To subscribe, send mail to [e-mail] with

    subscribe ncr53c810

    in the text.  You can unsubscribe by sending mail to the same address
    and including

    unsubscribe ncr53c810

    in the text.

Common Problems :

1.  Many people have encountered problems where the chip worked
    fine under DOS, but failed under Linux with a timeout on
    test 1 due to a lost interrupt.

    This is often due to a mismatch between the IRQ hardware
    jumper for a slot or mainboard device and the value set
    in the CMOS setup.  DOUBLE CHECK
        - The IRQ you are using is used only by your onboard NCR chip,
          or the slot an NCR board is installed in
        - Any main board jumpers selecting the IRQ for the onboard
          chip or slot match your CMOS setup.a
        - Some PCI mainboards have an "auto" assignment
          feature, which will not work.

    It may also be due to PCI INTB, INTC, or INTD being selected
    on a PCI board in a system which only supports PCI INTA.  If you
    are using an NCR board which has jumpers to select between PCI
    interrupt lines, make sure you are using INTA.

    Finally, PCI should be using level-sensitive rather
    than edge triggered interrupts.  Check that your board
    is jumpered for level-sensitive, and if that fails
    try edge-triggered because your system may be
    broken.

    This problem is especially common with Viglen some Viglen
    motherboards, where the mainboard IRQ jumper settings are
    NOT as documented in the manual.  I've been told that what
    claims to be IRQ5 is really IRQ9, your mileage will vary.

2.  Lockups / other problems occur when using an S3 928, or Tseng
        ET4000W32 PCI video board.

    There are hardware bugs in at least some revisions of these
    chips.  Don't use them.

3.  You get a message on boot up indicating that the I/O mapping
    was disabled because base address 0 bits 0..1 indicated a
    non I/O mapping

    This is due to a BIOS bug in some machines which results in
    dword reads of configuration regsisters returning the
    high and low 16 bit words swapped.

4.  Some systems have problems if PCI write posting, or CPU->
    PCI buffering are enabled.  If you have problems,
    disable these options.

5.  Some systems with the NCR SDMS software in an onboard BIOS

        ROM and in the system BIOS are unable to boot DOS.
    Disabling the image in one place should rectify this
    problem.

6.  If you encounter the message

    "scsi%d: IRQ0 not free, detaching"

    or

    "scsi%d: IRQ255 not free, detaching"

    The NCR chip had all 0 or 1 bits stored in the PCI configuration
    register.  Either you have configuration problems (see Common
    Problem 1), or you have a defective mainboard BIOS.

    As a work arround, you could edit drivers/scsi/ncr53c7,8xx.c,
    and change pci_init() so that you have

        irq = my_irq;

    before
            return normal_init (tpnt, board, chip, (int) base,
            (int) io_port, (int) irq, DMA_NONE, 1, bus, device_fn,
            options);

7.  Some systems have hideous, broken, BIOS chips.  Don't
    make any bug reports until you've made sure you have
    the newest ROM from your vendor.

8.  The command line overrides ncr53c810=xxx, etc. don't work.

    In stock kernels, this is because their entry points are not included
    in init/main.c, which is quite intentional :

        The driver makes no attempt to avoid autoprobing for a board
        where a command line override was used, so if an override
        is used where the board actually showed up to the PCI
        configuration routines, you'll have big problems.

        The only reason you would need an  override would be if the
        PCI hardware + BIOS were broken, in which case certain error
        recovery routines wouldn't work, rendering the override
        less than useful.

        Finally, nearly all of people who _think_ they need a command line
        override do because they get configuration or other error messages
        from the driver.  If the driver says you have a configuration
        problem, you have a broken system or a configuration problem
        and no override is going to fix this.

    If some one has gone and added the appropriate entry points to
    init/main.c for command line overrides, they are totally unsupported
    and may not work.

9.  Certain NCR boards (most notably Nexstor) which don't use an
    NCR BIOS get timeouts.  Some of these ROMs handle synchronous
    and transfers, negotiate for sync. transfers on power up,
    and leave the drives in an unknown state.  When the distribution
    Linux NCR driver attempts to talk with them, it gets timeouts
    and cannot recover because it won't do a bus reset or renegotiate.

    If you run into this problem, you can either disable
    synchronous transfers in the board's setup program, or
    upgrade to a newer ALPHA release of the NCR driver which
    will do synchronous negotiation.


Notes:
1.  CONFIG_PCI must be set

Section 4.14 : Seagate ST0x/Future Domain TMC-8xx/TMC-9xx
Supported and Unsupported Configurations :
Base addresses : 0xc8000, 0xca000, 0xcc000, 0xce000, 0xdc000, 0xde000
IRQs : 3, 5
DMA channels : DMA is not used
IO : memory mapped

Autoprobe : probes for address only, IRQ is assumed to be 5,
    requires installed BIOS.

Autoprobe Override :
Compile time : Define OVERRIDE to be the base address, CONTROLLER to
FD or SEAGATE as appropriate, and IRQ to the IRQ.

kernel command line : st0x=address,irq or tmc8xx=address,irq (only works
    for .99.13b and newer)

Antiquity Problems, fix by upgrading :

1.  Versions prior to the one in the Linux .99.12 kernel had a problem
    handshaking with some slow devices, where

    This is what happens when you write data out to the bus

    1.  Write byte to data register, data register is asserted to bus
    2.  time_remaining = 12us
    3.  wait while time_remaining > 0 and REQ is not asserted
    4.  if time_remaining > 0, assert ACK
    5.  wait while time remaining > 0  and REQ is asserted
    6.  deassert ACK

    The problem was encountered in slow devices that do the command
    processing as they read the command, where the REQ/ACK handshake
    takes over 12us - REQ didn't go false when the driver expected it
    to, so the driver ended up sending multiple bytes of data for
    each REQ pulse.

2.  With Linux .99.12, a bug was introduced when I fixed the arbitration
    code, resulting in failed selections on some systems.  This was
    fixed in .99.13.

Common Problems :

1.  There are command timeouts when Linux attempts to read the partition
    table or do other disk access.

    The board ships with the defaults set up for MSDOS, ie interrupts
    are disabled.  To jumper the board for interrupts, on the Seagate
    use jumper W3 (ST01) or JP3 (ST02) and short pins F-G to select
    IRQ 5.

2.  The driver can't handle some devices, particularly cheap SCSI
    tapes and CDROMs.

    The Seagate ties the SCSI bus REQ/ACK handshaking into the PC bus
    IO CHANNEL READY and (optionally) 0WS signals.  Unfortunately, it
    doesn't tell you when the watchdog timer runs out, and you have
    no way of knowing for certain that REQ went low, and may end up
    seeing one REQ pulse as multiple REQ pulses.

    Dealing with this means using a tight loop to look for REQ to
    go low, with a timeout incase you don't catch the transition due
    to an interrupt, etc.  This results in a performance decrease, so it
    would be undesireable to apply this to all SCSI devices.  Instead,
    it is selected on a per-device basis with the "borken" field for
    the given SCSI device in the scsi_devices array.  If you run into
    problems, you should try adding your device to the list of
    devices for which borken is not reset to zero (currently,
    only the TENEX CDROM drives).

3.  A future domain board (specific examples include the 840,841,
    880, and 881) doesn't work.

    A few of the Future domain boards use the Seagate
    register mapping, and have the MSG and CD bits of the
    status register flipped.

    You should edit seagate.h, swapping the definitions for
    STAT_MSG and STAT_CD, and recompile the kernel with
    CONTROLLER defined to SEAGATE and an appropriate
    IRQ and OVERRIDE specified.

4.  When attempting to fdisk your drive, you get error messages
    indicating that the HDIO_REQ or HDIO_GETGEO ioctl failed,
    or

    You must set heads sectors and cylinders.
    You can do this from the extra functions menu.


    See Section 5.4 : Disks : Partitioning

5.  After manually specifying the drive geometry, subsequent
    attempts to read the partition table result in partition
    boundary not on a cylinder boundary, physical and logical
    boundaries don't match, etc. error messages.

    See Section 5.4 : Disks : Partitioning


6.  Some systems which worked prior to .99.13 fail with newer
    versions of Linux.  Older versions of Linux assigned the
    CONTROL and DATA registers in an order different than that
    outlined in the Seagate documentation, which broke on some
    systems.  Newer versions make the assignment in the correct
    way, but this breaks other systems.

    The code in seagate.c looks like this now :

    cli();
    DATA = (unsigned char) ((1 << target) | (controller_type == SEAGATE ? 0x80 : 0x40));
    CONTROL = BASE_CMD | CMD_DRVR_ENABLE | CMD_SEL |
        (reselect ? CMD_ATTN : 0);
    sti();

    Changing this to

    cli();
    CONTROL = BASE_CMD | CMD_DRVR_ENABLE | CMD_SEL |
        (reselect ? CMD_ATTN : 0);
    DATA = (unsigned char) ((1 << target) | (controller_type == SEAGATE ? 0x80 : 0x40));
    sti()

    may fix your problem.

Defines :

FAST or FAST32 will use blind transfers where possible

ARBITRATE will cause the host adapter to arbitrate for the
    bus for better SCSI-II compatability, rather than just
        waiting for BUS FREE and then doing its thing.  Should
    let us do one command per Lun when I integrate my
    reorganization changes into the distribution sources.

SLOW_HANDSHAKE will allow compatability with broken devices that don't
    handshake fast enough (ie, some CD ROM's) for the Seagate
    code.

SLOW_RATE=x, x some number will let you specify a default
    transfer rate if handshaking isn't working correctly.

Section 4.15 : PAS16 SCSI
Supported and Unsupported Configurations :
Ports : 0x388, 0x384, 0x38x, 0x288
IRQs : 10, 12, 14, 15
    IMPORTANT : IRQ MUST be different from the IRQ used for the sound
    portion of the board.
DMA is not used for the SCSI portion of the board
IO : port mapped

Autoprobe : does not require BIOS

Autoprobe Override :
Compile time : Define PAS16_OVERRIDE to be an array of port, irq
tupples.  Ie

#define PAS16_OVERRIDE {{0x388, 10}}

for a board at port 0x388, IRQ 10.

kernel command line :
pas16=port,irq

Defines :
AUTOSENSE - if defined, REQUEST SENSE will be performed automatically
for commands that return with a CHECK CONDITION status.

PSEUDO_DMA - enables PSEUDO-DMA hardware, should give a 3-4X performance
increase compared to polled I/O.

PARITY - enable parity checking.  Not supported

SCSI2 - enable support for SCSI-II tagged queueing.  Untested


UNSAFE - leave interrupts enabled during pseudo-DMA transfers.  You
         only really want to use this if you're having a problem with
         dropped characters during high speed communications, and even
         then, you're going to be better off twiddling with transfersize.

USLEEP - enable support for devices that don't disconnect.  Untested.


Common problems :

1.  Command timeouts, aborts, etc.

    You should install the NCR5380 patches that I posted to the net
    some time ago, which should be integrated into some future alpha
    release.  These patches fix a race condition in earlier NCR5380
    driver cores, as well as fixing support for multiple devices on
    NCR5380 based boards.

    If that fails, you should disable the PSEUDO_DMA option by
    changing the #define PSEUDO_DMA line in drivers/scsi/pas16.c to #undef
    PSEUDO_DMA.

    Note that the later should be considered a last resort, because
    there will be a severe performance degradation.



Section 4.16 : Trantor T128/T128F/T228
Supported and Unsupported Configurations :
Base addresses :  0xcc000, 00xc8000, 0xdc000, 0xd8000
IRQs : none, 3, 5, 7 (all boards)
    10, 12, 14, 15 (T128F only)
DMA is not used.
IO : memory mapped

Autoprobe : works for all supported configurations, requires
    installed BIOS.

Autoprobe Override :
Compile time : Define T128_OVERRIDE to be an array of address, irq
tupples.  Ie

#define T128_OVERRIDE {{0xcc000, 5}}

for a board at address 0xcc000, IRQ 5.

The symbolic IRQs IRQ_NONE and IRQ_AUTO may be used.

kernel command line : t128=address,irq

-1 may be used for no irq, -2 for irq autoprobe.

Defines :
AUTOSENSE - if defined, REQUEST SENSE will be performed automatically
for commands that return with a CHECK CONDITION status.

PSEUDO_DMA - enables PSEUDO-DMA hardware, should give a 3-4X performance
increase compared to polled I/O.

PARITY - enable parity checking.  Not supported

SCSI2 - enable support for SCSI-II tagged queueing.  Untested


UNSAFE - leave interrupts enabled during pseudo-DMA transfers.  You
         only really want to use this if you're having a problem with
         dropped characters during high speed communications, and even
         then, you're going to be better off twiddling with transfersize.

USLEEP - enable support for devices that don't disconnect.  Untested.

Common Problems :
1.  Command timeouts, aborts, etc.

    You should install the NCR5380 patches that I posted to the net
    some time ago, which should be integrated into some future alpha
    release.  These patches fix a race condition in earlier NCR5380
    driver cores, as well as fixing support for multiple devices on
    NCR5380 based boards.

    If that fails, you should disable the PSEUDO_DMA option by
    changing the #define PSEUDO_DMA line in drivers/scsi/pas16.c to #undef
    PSEUDO_DMA.

    Note that the later should be considered a last resort, because
    there will be a severe performance degradation.

Section 4.17 : Ultrastor 14f (ISA), 24f (EISA), 34f (VLB)
Ports : 0x130, 0x140, 0x210, 0x230, 0x240, 0x310, 0x330, 0x340
IRQs : 10, 11, 14, 15
DMA channels : 5, 6, 7
IO : port mapped, bus master

Autoprobe : does not work for boards at port 0x310, BIOS not required.

Autoprobe override : compile time only, define PORT_OVERRIDE

Common Problems :
1.  The address 0x310 is not supported by the autoprobe code, and may
        cause conflicts if networking is enabled.

        Please use a different address.

2.  Using an Ultrastor at address 0x330 may cause the system to hang
        when the sound drivers are autoprobing.

        Please use a different address.

3.  Various other drivers do unsafe probes at various addresses, if you
        are having problems with detection or the system is hanging at
        boot time, please try a different address.

        0x340 is recommended as an address that is known to work.

4.  Linux detects no SCSI devices, but detects your SCSI hard disk
    on an Ultrastor SCSI board as a normal hard disk, and the
    hard disk driver refuses to support it.  Note that when this
    occurs, you will probably also get a message

    hd.c: ST-506 interface disk with more than 16 heads detected,
      probably due to non-standard sector translation.  Giving up.
      (disk %d: cyl=%d, sect=63, head=64)

    If this is the case, you are running the Ultrastor board in
    WD1003 emulation mode.  You have

    1.  Switch the ultrastor into native mode.  This is the
        recommended action, since the SCSI driver can be
        significantly faster than the IDE driver, especially with
        the clustered read/write patches installed.  Some users have
        sustained in excess of 2M/sec through the file system using
        these patches.

        Note that this will be necessary if you wish to use any non-
        hard disk, or more than two hard disk devices on the Ultrastor.

    2.  Use the kernel command line switch

        hd=cylinders,heads,sectors

        to override the default setting to bootstrap yourself,
        keeping number of cylinders <= 2048, number of heads <= 16,
        and number of sectors <= 255 such that cylinders * heads * sectors
        is the same for both mappings.

        You'll also have to manually specify the disk geometry when
        running fdisk under Linux.  Failure to do so will result in
        incorrect partition entries being written, which will work
        correctly with Linux but fail under MSDOS which looks at
        the cylinder/head/sector entries in the table.

        Once Linux is up, you can avoid the inconvience of having
        to boot by hand by recompiling the kernel with an appropriately
        defined HD_TYPE macro in include/linux/config.h.

Section 4.18 : Western Digital 7000
Supported Configurations :
BIOS Addresses : 0xce000
Ports : 0x350
IRQs : 15
DMA Channels : 6
IO : port mapped, bus master

Autoprobe :  requires installed BIOS

Common Problems :

1.  There are several revisisions of the chip and firmware.  Supposedly,
    revision 3 boards do not work, revision 5 boards do,
    chips with no suffix do not work, chips with an 'A' suffix do.

2.  The board supports a few BIOS addresses which aren't on the list
    of supported addresses.  If you run into this situation,
    please use one of the supported addresses and submit a bug
    report as outlined in Section 2, "Bug Reports"

Section 4.19 : AM53/79C974 (ALPHA)
    ftp://tsx-11.mit.edu/pub/linux/ALPHA/scsi/AM53C974-0.3.tar.gz

Supported Configurations :
Ports : all
IRQs : all
DMA Channels : 6
IO : port mapped, bus master (unintelligent)



Section 5 : Disks

This section gives information that is specific to disk drives.

Section 5.1 : Supported and Unsupported Hardware

All direct access SCSI devices with a block size of 256, 512, or
1024 bytes should work.  Other block sizes will not work (Note
that this can often be fixed by changing the block and/or
sector sizes using the MODE SELECT SCSI command)

Sector size refers to the number of data bytes allocated per sector
on a device, ie CDROMs use a 2048 byte sector size.

Block size refers to the size of the logical blocks used to interface
with the device.  Although this is usually identical to sector size,
some devices map multiple smaller physical sectors (ie, 256 bytes
in the case of 55M Syquest drives) to larger logical blocks or
vice versa (ie, 512 byte blocks on SUN compatable CDROM drives).

Removeable media devices, including Bernoulis, flopticals, MO drives,
and Syquests.

In theory, drives up to a terrabyte in size should work.  There is
definately no problem with tiny 9G drives.

Section 5.2 : Common Problems

Section 5.2.1 : Cylinder > 1024 message.

    When partitioning, you get a warning message about "cylinder > 1024"
    or you are unable to boot from a partition including a logical
    cylinder past logical cylinder 1024.

    This is a BIOS limitation.

    See Section 5.4 Disk Geometry and Partitioning for an explanation.

Section 5.2.2 :  You are unable to partition "/dev/hd*"

    /dev/hd* aren't SCSI devices, /dev/sd* are.

    See Section 5.3, Device files, and Section 5.4, Disk
    Geometry and Partitioning
    for the correct device names and partitioning procedure.

Section 5.2.3 :   Unable to eject media from a removeable media drive.

    Linux attempts to lock the drive door when a piece of
    media is mounted to prevent filesystem corruption due to
    an inadvertant media change.

    Please unmount your disks before ejecting them.


Section 5.2.4 : Unable to boot using LILO from a SCSI disk

    In some cases, the SCSI driver and BIOS will disagree
    over the correct BIOS mapping to use, and will result
    in LILO hanging after 'LI' at boot time and/or
    other problems.

    To workarround this, you'll have to determine your BIOS
    geometry mapping used under DOS, and make an entry for
    your disk in /etc/lilo/disktab.

    Alternatively, you may be able to use the "linear" configuration
    file option.

Section 5.2.5 : Fdisk responds with

            You must set heads sectors and cylinders.
            You can do this from the extra functions menu.

        and disk geometry is not 'remembered' when fdisk is rerun.

    See Section 5.4 : Partitioning

Section 5.2.6 : Only one drive is detected on a bridge board with
    multiple drives connected.

    Linux won't search LUNs past zero on SCSI devices which
    predate ANSI SCSI revision 1.  If you wish devices on
    alternate LUNs to be recognized, you will have to modify
    drivers/scsi/scsi.c:scan_scsis().

Section 5.2.7 : System hangs when swapping

    We think this has been fixed, try upgrading to 1.1.38.

Section 5.2.8 : Connor CFP1060S disks get corrupted

    This is due to a microcode bug in the read-ahead and
    caching code.

    From Soenke Behrens of Conner tech. support :

During the past few weeks, we got several calls from customers stating
that they had severe problems with Conner CFP1060x 1GB SCSI drives
using the Linux operating system. Symptoms were corrupt filesystems
(damaged inodes) reported by e2fsck on each system boot and similar
errors.

There is now a fix available for customers with a CFP1060x (microcode
revisions 9WA1.62/1.66/1.68) and Linux. To apply the upgrade, you
will need a DOS boot disk and ASPI drivers that can access the hard
drive. The upgrade downloads new queuing and lookahead code into the
non-volatile SCSI RAM of the drive.

If you are experiencing problems with a disk that has microcode
revision 9WA1.60, you will have to contact your nearest Conner service
centre to get the disk upgraded. The microcode revision can be found
on the label of the drive and on the underside of the drive on a label
on one of the ICs.

If you are confident that you can perform the upgrade yourself, please
contact Conner Technical Support and have your microcode revision
ready. Conner Technical Support Europe can be reached on [phone],
Conner Technical Support in the USA can be reached on 1-800-4CONNER.

Regards
Soenke Behrens
European Technical Support

Section 5.3 : Device Files

SCSI disks use block device major 8, and there are no "raw" devices
ala BSD.

16 minor numbers are allocated to each SCSI disk, with minor % 16 == 0
being the whole disk, minors  1 <= (minor % 16) <= 4 the four primary
partitions, minors 5 <= (minor % 16) <= 15 any extended partitions.

Ie, a configuration may work out like this (with one host adapter)

Device            Target, Lun        SCSI disk
84M Seagate         0    0        /dev/sda
SCSI->SMD bridge disk 0    3    0        /dev/sdb
SCSI->SMD bridge disk 1    3    1        /dev/sdc
Wangtek tape        4    0        none
213M Maxtor        6    0        /dev/sdd

Etc.

The standard naming convention is

/dev/sd{letter} for the entire disk device ((minor % 16) == 0)
/dev/sd{letter}{partition} for the partitions on that device
    (1 <= (minor % 16) <= 15)

Ie

/dev/sda    block device major 8 minor 0
/dev/sda1    block device major 8 minor 1
/dev/sda2    block device major 8 minor 2
/dev/sdb    block device major 8 minor 16

etc.

Section 5.4 : Partitioning

You can partition your SCSI disks using the partitioning program
of your choice, under DOS, OS/2, Linux or any other operating
system supporting the standard partitioning scheme.

The correct way to run the Linux fdisk program is by specifying the
device on the command line. Ie, to partition the first SCSI disk,

    fdisk /dev/sda

If you don't explicitly specify the device, the partitioning program
may default to /dev/hda, which isn't a SCSI disk.

In some cases, fdisk will respond with

    You must set heads sectors and cylinders.
    You can do this from the extra functions menu.

    Command (m for help):

and/or give a message to the effect that the HDIO_REQ or
HDIO_GETGEO ioctl failed.  In these cases, you must
manually specify the disk geometry as outlined in Subsection
5.5 : Disk Geometry when running fdisk, and also in /etc/disktab
if you wish to boot kernels off that disk with LILO.

If you have manually specified the disk geometry, subsequent
attempts to run fdisk will give the same error message.  This
is normal, since PCs don't store the disk geometry information
in the partition table. In and of itself, will cause _NO PROBLEMS_,
and you will have no problems accessing partitions you created on
the drive with Linux.  Some vendors' poor installation code will
choke on this, in which case you should contact your vendor
and insist that they fix the code.

In some cases, you will get a warning message about a partition ending
past cylinder 1024.  If you create one of these partitions, you will
be unable to boot Linux kernels off of that partition using LILO.  Note,
however, that this restriction does not preclude the creation of a
root partition partially or entirely above the 1024 cylinder mark,
since it is possible to create a small /boot partition below the
1024 cylinder mark or to boot kernels off existing partitions.

Section 5.5 : Disk Geometry

Under Linux, each disk is viewed as the SCSI host adapter sees it :
N blocks, numbered from 0 to N-1, all error free, where as DOS/BIOS
predate intelligent disks and apply an arbitrary head / cylinder /
sector mapping to this linear addressing.

This can pose a problem when you partition the drives under Linux,
since there is no portable way to get DOS/BIOS's idea of the mapped
geometry.  In most cases, a HDIO_GETGEO ioctl() can be implemented
to return this mapping.  Unfortunately, when the vendor (ie Seagate)
has chosen a perverse, non-standard, and undocumented mapping, this
is not possible and geometry must be manually specified

If manual specification of the is required, you have one of several
options :

1.  If you don't care about using DOS, or booting kernels from the
    drive with LILO, create a translation such that heads * cylinders *
    sectors * 512 < size of your drive in bytes (a megabyte is defined
    as 2^20 bytes).


    1 <= heads <= 256
    1 <= cylinders <= 1024
    1 <= sectors <= 63

2.  Use the BIOS mapping.  In some cases, this will mean reconfiguring the
    disk so that it is at SCSI ID 0, and disabling the second IDE drive (if you have one).

    You can either use a program like NU, or you can use the following
    program :

begin 664 dparam.com
MBAZ``##_B+^!`+N!`(H'0SP@=/D\,'5:@#]X=`6`/UAU4(!_`3AU2H!_`P!U
M1(I7`H#J,(#Z`7<Y@,*`M`C-$PCD=3-14HC()#\PY.@R`.@J`%J(\/[`,.3H
M)0#H'0!8AL2Q!M+L0.@7`+K"`;0)S2'#NIP!ZR"ZQ0'K&[K5`>L6N]T!,=*Y
M"@#W\8#",$N(%PG`=>^)VK0)S2'#=7-A9V4Z(&1P87)A;2`P>#@P#0H@("!O
L<B`@9'!A<F%M(#!X.#$-"B1);G9A;&ED(&1R:79E#0HD("`D```````D``!O
`
end

    When run it prints the sectors, heads, and cylinders of the
    drive whose BIOS address was specified on the command line (0x80
    is the first disk, 0x81 the second).

    Ie, dparam 0x80
    60    17    1007

Would mean that C: had 60 sectors, 17 heads, and 1007 cylinders.

Section 6 : CD ROMs

This section gives information that is specific to cdrom drives.

Section 6.1 : Supported and Unsupported Hardware

SCSI CDs with a block size of 512 or 2048 bytes should work.  Other
block sizes will not work.

Section 6.2 : Common Problems

Section 6.2.1 : Unable to mount cdrom.

        The correct syntax to mount an ISO-9660 CDROM is

        mount -t iso9660 /dev/sr0 /mount_point -o ro

        Note that for this to work, you must have the kernel
        configured with support for SCSI, your host adapter,
        the SCSI CDROM driver, and the iso9660 filesystem.

    Note that as of Linux 1.1.32, read-only devices such
    as CDROMs CANNOT be mounted with the default read/write
    options.

Section 6.2.2 : Unable to eject cdrom.

    Linux attempts to lock the drive door when a piece of
    media is mounted to prevent filesystem corruption due to
    an inadvertant media change.

Section 6.2.3 : Unable to play audio.

    The programs Workman or xcdplayer will do this for you.

Section 6.2.4 :  Workman or Xcdplayer do not work.

    The functions to control audio functions are part of the
SCSI-II command set, so any drive that is not SCSI-II will probably
not work here.  Also, many SCSI-I and some SCSI-II CDROM drives use a
proprietary command set for accessing audio functions instead of the
SCSI-II command set.  For NEC drives, there is a version of xcdplayer
specially adapted to use this command set floating around - try
looking on tsx-11.mit.edu in pub/linux/BETA/cdrom.

    These programs may work with some of the non-SCSI cdrom drives
if the driver implements the same ioctls as the scsi drivers.

Section 6.2.5: Additional drives on CD ROM changers do not work

    Most CD changers assign each disc to a logical unit.  Insure that
you have special files made for each platter (see Section 6.3 : Device Files)
and see Section 1.10 : LUNS other than 0 don't work

Section 6.3 : Device Files

SCSI CD ROMs use major 11.

Minors are allocated dynamically (See Section 5 : Disks, Subsection 5.3 :
Device Files for an example) with the first CDROM found being minor 0,
the second minor 1, etc.

The standard naming convention is

/dev/sr{digit}, although some distributions have used /dev/scd{digit}, with
examples being

/dev/sr0    /dev/scd0
/dev/sr1    /dev/scd1

Section 7 : Tapes

This setion gives information that is specific to scsi tape drives.

Section 7.1 : Supported and Unsupported Hardware

Drives using both fixed and variable length blocks smaller than the
the driver buffer length (set to 32K in the distribution sources) are
supported.

Parameters (block size, buffering, density) are set with ioctls
(usually with the mt program), and remain in effect after the
device is closed and reopened.

Virtually all drives should work, including :
    Archive Viper QIC drives, including the 150M and 525M models
    Exabyte 8mm drives
    Wangtek 5150S drives
    Wangdat DAT drives

Section 7.2 : Common Problems

Section 7.2.1 : Tape drive not recognized at boot time.

    Try booting with a tape in the drive.

Section 7.2.2 :  Tapes with multiple files cannot be read properly.

    When reading a tape with multiple files, the first tar
    is successful, a second tar fails silently, and retrying
    the second tar is successful.

    User level programs, such as tar, don't understand file marks.
    The first tar reads up until the end of the file.  The second
    tar attempts to read at the file mark, gets nothing, but the
    tape spaces over the file mark.  The third tar is successful
    since the tape is at the start of the next file.

    Use mt on the no-rewind device to space forward to the next file.


Section 7.2.3 :  Decompression fails.

    Decompressing programs cannot handle the zeros padding the
    last block of the file.

    To prevent warnings and errors, wrap your compressed files
    in a .tar file - ie, rather than doing

    tar cfvz /dev/nrst0 file.1 file.2 ...

    do

    tar cfvz tmp.tar.z file.1 file.2 ...

    tar cf /dev/nrst0 tmp.tar.z

Section 7.2.4 :  Problems taking tapes to/from other systems.

    You can't read a tape made with another operating system or
    another operating system can't read a tape written in Linux.

    Different systems often use different block sizes.  On a
    tape device using a fixed blocksize, you will get errors
    when reading blocks written using a different block size.

    To read these tapes, you must set the blocksize of
    the tape driver to match the blocksize used when
    the tape was written, or to variable.

    NOTE : this is the hardware block size, not the blocking
    factor used with tar, dump, etc.

    You can do this with the mt command -


        mt setblk <size>

    or

        mt setblk 0

    to get variable block length support.


    Note that these mt flags are NOT supported under the GNU version
    of mt which is included with some Linux distributions.  Instead,
    you must use the BSD derrived Linux SCSI mt command.  Source
    should be available from

        tsx-11.mit.edu:/pub/linux/ALPHA/scsi

    Also note that by default, ST_BUFFER_BLOCKS (defined
    in /usr/src/linux/drivers/scsi/st_options.h in newer
    kernels, st.c in older kernels) is set to allow for
    a 32K maximum buffer size; you'll need to edit the source
    to use larger blocks.

Section 7.2.5 :  "No such device" error message.

    All attempts to access the tape result in a

    "No such device"

    or similar error message.  Check the type of
    your tape device - it MUST be a character device with
    major and minor numbers matching those specified in subsection
    C, Device Files.

Section 7.2.6 : Tape reads at a given density work, writes fail

    Many tape drives support reading at lower densities
    for compatability with older harware, but will not
    write at those same densities.

    This is especially the case with QIC drives, which
    will read old 60M tapes but only write new 120, 150,
    250, and 525M formats.

Section 7.2.6 : Repositioning the tape locks out access to all SCSI devices

    This is most common with SCSI drivers which only support one
    outstanding command at a time (see Section 9.5 : Multiple
    devices for an explanation, and Section : Driver feature comparison
    to see which drivers suffer from this limitation), although there may
    be a few tape drives out there which refuse to disconnect.

    In either case, you can work arround the problem by editing
    drivers/scsi/st.c and adding a

        #define ST_NOWAIT

    at the top and rebuilding the kernel.

    Note that this will defer error condition reporting until the
    next SCSI command is executed.  For this reason, you may want to
    do something like a

        mt status

    after a mt file positioning command so you don't overwrite tape
    files if the positioning command failed.

    You may also wish to consider changing to a better-supported SCSI
    board or newer tape drive if you need to use this workarround
    and are writing multiple files to tapes.

Section 7.3 : Device Files

SCSI tapes use character device major 9.

Due to constraints imposed by Linux's use of a sixteen bit dev_t with
only eight bits allocated to the minor number, the SCSI tape minor
numbers are assigned dynamically starting with the lowest SCSI HOST/ID/LUN.

Rewinding devices are numbered from 0 - with the first
SCSI tape, /dev/rst0 being c 9 0, the second /dev/rst1 c 9 1, etc.
Non-rewinding devices have the high bit set in the minor number,
ie /dev/nrst0 is c 9 128.

The standard naming convention is
/dev/nst{digit}     for non-rewinding devices
/dev/st{digit}        for rewinding devices

Section 8 : Generic

This information gives information that is specific to the generic
scsi driver.

Section 8.1 : Supported Hardware

The Generic SCSI device driver provides an interface for sending
SCSI commands to all SCSI devices - disks, tapes, CDROMs, media
changer robots, etc.

Everything electrically compatable with your SCSI board should work.

Section 8.2 : Common Problems

None :-).

Section 8.3 : Device Files

SCSI generic devices use character major 21.  Due to constraints
imposed by Linux's use of a 16 bit dev_t, minor numbers are dynamically
assigned from 0, one per device, with

/dev/sg0

corresponding to the lowest numerical target/lun on the first
SCSI board.

Section 9 : Buyers' Guide

    A frequent question is:

    "Linux supports quite a number of different boards, so which
scsi host adapter should I get."

    The answer depends upon how much performance you expect or need,
motherboard, and the scsi peripherals that you plan on attaching to
your machine.

Section 9.1 : Transfer types

    The biggest factor affecting performance (in terms of throughput
and interactive response time during SCSI I/O) is the transfer type used.
The table below lists the various transfer types, the effects they have
on performance, and some recomendations as to their use.

Transfer type    Description / Performance / Recomendedations
Pure        A pure polled I/O board will use the CPU to handle
Polled        all of the SCSI processing, including the REQ/ACK
        handshaking.

        Even a fast CPU will be slower handling the REQ/ACK
        handshake sequence than a simple finite state machine,
        resulting in peak transfer rates of about 150K/sec on
        a fast machine, perhaps 60K/sec on a slow machine
        (through the filesystem).

        The driver also must sit in a tight loop as long as the
        SCSI bus is busy, resulting in near 100% CPU utilitization
        and extremely poor responsiveness during SCSI I/O.
        Slow CDROMs which don't disconnect/reconnect will kill
        interactive performance with these boards.

        Not recommended.

Interlocked    Boards using interlocked polled I/O are essentially
Polled        the same as pure polled I/O boards, only the SCSI REQ/ACK
        handshaking signals are interlocked with the PC bus
        handshaking signals.  All SCSI processing beyond
        the handshaking is handled by the CPU.

        Peak transfer rates of 500-600K/sec through the
        filesystem are possible on these boards.

        As with pure polled I/O boards, the driver must sit
        in a tight loop as long as the SCSI bus is busy,
        resulting in CPU utilization dependant on the
        transfer rates of the devices, and when they
        disconnect/reconnect.  CPU utilization may vary
        between 25% for single speed CDs which handle
        disconnect/reconnect properly to 100% for faster
        drives or broken CD ROMs which fail to disconnect/reconnect.

        On my 486-66, with a T128, I use 90% of my CPU time to
        sustain a throughput of 547K/sec on a drive
        with a headrate of 1080K/sec with a T128 board.

        Sometimes acceptable for slow tapes and CDROMs when
        low cost is essential.

FIFO         Boards using FIFO polled I/O put a small (typically 8K)
Polled        buffer between the CPU and the SCSI bus, and often implement
        some amount of intelligence.  The net effect is that
        the CPU is only tied up when it is transfering data
        at top speed to the FIFO and when it's handling the
        rest of the interrupt processing for FIFO empty conditions,
        disconnect/reconnect, etc.

        Peak transfer rates should be sufficient to handle
        most SCSI devices, and have been measured at up
        to 4M/sec using raw SCSI commands to read 64K
        blocks on a fast Seagate Barcuda with an Adaptec
        1520.

        CPU utilization is dependant on the transfer
        rates of the  devices, with faster devices generating
        more interrupts per unit time which require more CPU
        processing time.   Although CPU usage may be high
        (perhaps 75%) with fast devices, the system usually
        remains usable.  These boards will provide excellent
        interactive performance with broken devices which
        don't disconnect/reconnect (typically cheap CDROM
        drives)

        Recommended for persons on a budget.

Slave          Drivers for boards using slave DMA program the PC's
DMA        DMA controller for a channel when they do a data transfer,
        and return control to the CPU.

        Peak transfer rates are usually handicapped
        by the poor DMA controller used on PCs,
        with one such 8-bit board having problems
        going faster than 140-150K/sec with one mainboard.

        CPU utilization is very reasonable, slightly
        less than what is seen with FIFO polled I/O boards.
        These boards are very tollerant of broken devices
        which don't disconnect/reconnect (typically cheap
        CSG limitDROM drives).

        Acceptable for slow CDROM drives, tapes, etc.

Busmastering    These boards are intelligent.  Drivers
DMA         for these boards throw a SCSI command, the destination
        target and lun, and where the data should end up
        in a structure, and tell the board "Hey, I have
        a command for you."  The driver returns control
        to various running programs, and eventually the
        SCSI board gets back and says that it's done.

        Since the intelligence is in the host adapter
        firmware and not the driver, drivers for these
        boards typically support more features - synchronous
        transfers, tagged queing, etc.

        With the clustered read/write patches, peak transfer
        rates through the file system approach 100% of head rate
        writing, 75% reading.

        CPU utilization is minimal, irregardless of
        I/O load, with a measured 5% CPU usage while
        accessing a double speed CDROM on an Adaptec 1540
        and 20% while sustaining a 1.2M/sec transfer rate
        on a SCSI disk.

        Recommended in all cases where money is not extremely
        tight, the main board is not broken (some broken main boards
        do not work with bus masters), and applications where time
        to data is more important than throughput are not being run
        (bus master overhead may hit 3-4ms per command).

Section 9.2 : Scatter/gather

    The second most important driver/hardware feature with respect
to performance is support for scatter/gather I/O.  The overhead of executing
a SCSI command is significant - on the order of milliseconds. Intelligent bus
masters like the Adaptec 1540 may take 3-4ms to process a SCSI command before
the target even sees it.  On unbuffered devices, this overhead is allways enough
to slip a revolution, resulting in a transfer rate of about 60K/sec
(assuming a 3600RPM drive) per block transfered at a time.  So, to maximize
performance, it is necessary to minimize the number of SCSI commands needed
to transfer a given amount of data by transfering more data per command.  Due
to the design of the Linux buffer cache, contiguous disk blocks are not
contiguous in memory. With the clustered read/write patches, 4K worth of
buffers are contiguous.  So, the maximum amount of data which can
be transfered per SCSI command is going to be 1K * # of scatter/gather
regions without the clustered read/write patches, 4K * # of regions
with.  Experimentally, we've determined that 64K is a reasonable
amount to transfer with a single SCSI command - meaning 64 scatter/gather
buffers with clustered read/write patches, 16 without.  With the
change from 16K to 64K transfers, we saw an improvement from
50% of headreate, through the filesystem, reading and writing,
to 75% and 100% respectively using an Adaptec 1540 series board.

Section 9.3 : Mailbox vs. non-mailbox

    A number of intelligent host adapters, such as the Ultrastor, WD7000,
Adaptec 1540, 1740, and BusLogic boards have used a mailbox-metaphor
interface, where SCSI commands are executed by putting a SCSI command
structure in a fixed memory location (mailbox), signaling the board (ie,
raising the outgoing mail flag), and waiting for a return (incoming mail).
With this high level programming interface, users can often upgrade to a
newer board revision to take advantage of new features, such as FAST +
WIDE SCSI, without software changes.  Drivers tend to be simpler to
implement, may implement a larger feature set, and may be more stable.

Other intelligent host adapters, such as the NCR53c7/8xx family,
and Adaptec AIC-7770/7870 chips (including the 274x, 284x, and 2940
boards) use a lower level programming interface.  This may prove
faster since processing can be shifted between the board's processor
and faster host CPU, allow better flexibility in implementing certain
features (ie, target mode for arbitrary devices), and these boards
can be built for less money (In some cases, this is passed on to
the consumer (ie, most NCR boards)).  On the down side, drivers
tend to be more complex (read : there is more potential for bugs),
and must be modified to take advantage of the features present on
newer chips.

Section 9.4 : Bus types

    Bus type is the next thing to consider, with choices including ISA,
EISA, VESA, and PCI.  Marketing types often spout of absurd bandwidth
numbers based on burst transfer rates and fiction, which isn't very
useful.  Instead, I've chosen to state "real-world" numbers based on
measured performance with various peripherials.

Bus    Bandwidth, description,
ISA    Bandwidth is slightly better than 5M/sec for  busmastering
    devices.  With an ISA bus, arbitration for busmasters is performed
    by the venerable 8237 third party DMA controller, resulting in
    relatively high bus aquisition times.  Interrupt drivers are
    tri-state and edge triggered, meaning interrupts cannot be
    shared. Generally, ISA is unbuffered, meaning the host/memory
    bus is tied up whenever a transfer is occuring. No mechanism
    is provided to prevent bus-hogging.

VESA    Bandwidth is about 30M/sec.  Some VESA systems run the bus out
    of spec, rendering them incompatable with some boards, so this
    should be taken into consideration before purchasing hardware
    without a return guarantee.  Generally, VESA is unbuffered, meaning
    meaning the host/memory bus is tied up whenever a transfer is
    occuring.

EISA    Bandwidth is about 30M/sec, with busmastering operations generally
    being faster than VESA.  Some EISA systems buffer the bus, allowing
    burst transfers to the faster host/memory bus and minimizing impact
    on CPU performance.  EISA interrupt drivers may be either tri-state
    edge-triggered or open collector level-active, allowing interrupt
    sharing with drivers that support it.  Since EISA allocates a
    separate address space for each board, it is usually less prone to
    resource conflicts than ISA or VESA.

PCI    Bandwidth is about 60M/sec.  Most PCI systems implement write
    posting buffers on the host bridge, allowing speed mismatches
    on either side to have a minimum impact on bus/CPU performance.
    PCI interrupt drivers are open collector level-active, allowing
    interrupt sharing with drivers that support it. Mechanisms
    are provided to prevent bus hogging, and for both master and
    slave to suspend a bus-mastering operation.

    Since PCI provides a plug-n-play mechanism with writeable
    configuration registers on every board, in a separate address space,
    a propperly implemented PCI system is plug-and play.

    PCI is extremely strict as to trace length, loading, mechanical
    specifications, etc. and ultimately should be more reliable than
    VESA or ISA.

    In summary, PCI is the best PC bus, although it does
    have its dark side.  PCI is still in its infancy, and although
    most manufacturers have ironed out the problems, there is
    still stock of older, buggy PCI hardware and broken main
    BIOSes.  For this reason, I _strongly_ recommend a return
    guarantee on the hardware.  While the latest PCI mainboards
    are truly plug-and-play, older PCI boards may require the
    user to set options with both jumpers and in software (ie,
    interrupt assignments).  Although many users have
    resolved their PCI problems, it has taken time and for this
    reason I cannot recommend a PCI purchase if having the
    system operational is extremely time critical.

    For many slower SCSI devices, such as disks with head rates
arround 2M/sec or less, CDROMs, and tapes, there will be little difference
in throughputs with the different PC bus interfaces.  For faster contemporary
SCSI drives (Typical high end multi-gigabyte drives have a head rate of
4-5M/sec, and at least one company is currently ALPHA testing a parallel
head unit with a 14M/sec head rate), throughput will often be significantly
better with controllers on faster busses, with one user noting a 2.5 fold
performance improvement when going from an Adaptec 1542 ISA board to a
NCR53c810 PCI board.

    With the exception of situations where PCI write-posting or a
similar write-buffering mechanism is being used, when one of the busses in
your system is busy, all of the busses will be unaccessable.  So, although
bus saturation may not be interfering with SCSI performance, it may have a
negative effect on interactive performance.  Ie, if you have a 4M/sec SCSI
disk under ISA, you'll have lost 80% of your bandwidth, and in an
ISA/VESA system would only be able to bitblt at 6M/sec.  In most cases,
a similar impact on processing jobs in the background would also be felt.

    Note that having over 16M of memory does not preclude using
an ISA busmastering SCSI board.  Unlike various broken operating
systems, Linux will double buffer when using a DMA with an ISA controller
and a transfer is ultimately destined for an area above 16M.  Performance
on these transfers only suffers by about 1.5%, ie not noticably.

    Finally, the price difference between bus masters offered with the
different bus interfaces is often minimal.

    With all that in mind, based on your priorities you will have
certain bus preferences

    Stability, time critical installations,      EISA ISA VESA PCI
        and poor return policies
    Performance, and typical hobbiest        PCI EISA VESA ISA
        installations


     As I pointed out earlier, bus mastering versus other transfer modes is
going to have a bigger impact on total system performance, and should be
considered more important than bus type when purchasing a SCSI controller.

Section 9.5 : Multiple devices

    If will you have multiple devices on your SCSI bus, you may
want to see whether the host adapter/driver that you are considering supports
more than one outstanding command at one time.  This is almost
essential if you'll be running a tape drive, and very desireable
if you are mixing devices of different speeds, like a CD ROM and a disk
drive.  If the linux driver only supports one outstanding command, you may
be locked out of your disk drive while a tape in the tape drive is rewinding or
seeking to end of media (perhaps for half an hour).  With two
disk drives, the problem will not be as noticeable, allthough
throughput would approach the average of the two transfer rates
rather than the sum of the two transfer rates.

Section 9.6: SCSI-I, SCSI-II, SCSI-III FAST and WIDE options, etc.

    Over the years, SCSI has evolved, with new revisions of the standard
introducing higher transfer rates, methods to increase throughput, standardized
commands for new devices, and new commands for previously supported devices.

    In and of themselves, the revision levels don't really mean anything.
Excepting minor things like SCSI-II not allowing the single initiator option
of SCSI-I, SCSI is backwards compatable, with new features being introduced
as options and not mandatory.  So, the descision to call a SCSI adapter
SCSI, SCSI-II, or SCSI-III is almost entirely a marketing one.

Section 9.7 : Driver feature comparison

Driver feature comparison (supported chips are listed in parenthesis)

Driver                  Simultaneous    SG         > 1
        Transfer mode        Commands    limit        Boards
                    total/LUN
AM53C974    Busmastering DMA    12s/1s        255s        Y
aha152x          FIFO(8k) Polled           7s/1s        255s        N
    (AIC6260,
    AIC6360)
aha1542       Busmastering DMA     8s/1s        16        Y
aha1740          Busmastering DMA     32s        16        N
aha274x        Busmastering DMA    4s/1s        255s        Y
BusLogic    Busmastering DMA    192/31        128s, 8192h    Y
(values are for BT-948/958/958D, older boards support fewer commands)
eata_dma        Busmastering DMA        64s/16s         64s             Y
fdomain        FIFO(8k) Polled        1s        64s        N
    (TMC1800,     except TMC18c30
    TMC18c30,    with 2k FIFO
    TMC18c50,
    TMC36c70)

in2000*        FIFO(2k) Polled        1s        255s        N
g_NCR5380    Pure Polled         16s/2s        255s        Y
    (NCR5380,
    NCR53c80,
    NCR5381,
    NCR53c400)
gsi8*        Slave DMA        16s/2s        255s
    (NCR5380)
PAS16        Pure Polled        16s/2s        255s        Y
    (NCR5380)    or Interlocked Polled
        (fails on some systems!)
seagate        Interlocked Polled    1s/1s        255s        N
wd7000          Busmastering DMA    16s/1s        16         Y
t128        Interlocked Polled    16s        255s        Y
    (NCR5380)
qlogic        Interlocked Polled    1s/1s        255s        N
ultrastor     Busmastering DMA    16s/2s        32        Y
53c7,8xx    Busmastering DMA
    (NCR53c810,
     NCR53c815,
     NCR53c820,
     NCR53c825)
    rel5                 1s/1s        127s        N
    rel10                8s/1s        127s        Y


Notes :
1.  drivers flagged with an '*' are not included with the
    distribution kernel, and binary boot images may be unavailable.

2.  numbers suffixed with an 's' are arbitrary limits set in software
    which may be changed with a compile time define.

3.  hardware limits are indicated by an 'h' suffix, and may differ
    from the software limits currently imposed by the Linux drivers.

4.  unsuffixed numbers may indicate either hard or soft limits.

5.  rel5 of the NCR53c810 driver is included in the stock 1.2.x and
    1.3.x kernels; rel10 is available via anonymous FTP.

6.  With the exception of the AM53C974, the busmastering DMA boards
    are intelligent; with the NCR executing microcode from main memory,
    the AIC7770 executing microcode from on-chip RAM, and the rest using
    a mailbox-style interface.

Section 9.8 : Board comparison

Board            Driver        Bus    Price    Notes
Adaptec AIC-6260    aha152x        ISA        chip, not board
Adaptec AIC-6360    aha152x        VLB        chip, not board
    (Used in most
    VESA/ISA multi-IO
    boards with SCSI,
    Zenon mainboards)
Adaptec 1520        aha152x        ISA
Adaptec 1522        aha152x        ISA    $80    1520 w/FDC
Adaptec 1510        aha152x        ISA        1520 w/out boot ROM,
                            won't autoprobe.
Adaptec 1540C        aha1542        ISA
Adaptec 1542C        aha1542        ISA        1540C w/FDC
Adaptec 1540CF        aha1542        ISA        FAST SCSI-II
Adaptec 1542CF        aha1542        ISA    $200    1540CF w/FDC
Adaptec 1640        aha1542        MCA

Adaptec 1740        aha1740        EISA        discontinued
Adaptec 1742        aha1740        EISA        discontinued, 1740
                            w/FDC
Adaptec 2740        aha274x        EISA
Adaptec 2742        aha274x        EISA        w/FDC
Adaptec 2840        aha274x        VLB
Adaptec 2842        aha274x        VLB        w/FDC
Adaptec 2940        aha274x        PCI
Allways IN2000        in2000        ISA
BusLogic BT-948        BusLogic    PCI    $180    Ultra SCSI
BusLogic BT-958        BusLogic    PCI    $230    Wide Ultra SCSI
(see section 4.8 for additional BusLogic board descriptions)
DPT     PM2011        eata_dma    ISA        FAST SCSI-II
    PM2012A        eata_dma    EISA        FAST SCSI-II
    PM2012B        eata_dma    EISA        FAST SCSI-II
    PM2021        eata_dma    ISA    $245    FAST SCSI-II
     PM2022        eata_dma    EISA    $449    FAST SCSI-II
                            active termination
    PM2024        eata_dma    PCI    $395    FAST SCSI-II
                            active termination
    PM2122        eata_dma    EISA    $595    FAST SCSI-II
                            active termination
    PM2124        eata_dma    PCI    $595    FAST SCSI-II
                            active termination
    PM2322        eata_dma    EISA        FAST SCSI-II
                            active termination
    PM3021        eata_dma    ISA    $1595    FAST SCSI-II
                            multichannel
                            raid/simm sockets
                            active termination
    PM3122        eata_dma    EISA    $1795    FAST SCSI-II
                            multichannel/raid
                            active termination
    PM3222        eata_dma    EISA    $1795    FAST SCSI-II
                            multichannel
                            raid/simm sockets
                            active termination
    PM3224        eata_dma    PCI    $1995    FAST SCSI-II
                            multichannel
                            raid/simm sockets
                            active termination
DTC 3290        aha1542        EISA        Although it should work,
                            due to documentation
                            release polcies, DTC
                            hardware is unsupported
DTC 3130        53c7,8xx    PCI        '810
DTC 3130B        53c7,8xx    PCI        '815
DTC 3292        aha1542        EISA        3290 w/FDC
DTC 3292        aha1542        EISA        3290 w/FDC
Future Domain 1680    fdomain        ISA        FDC
Future Domain 3260    fdomain        PCI
NCR53c810 (boards sold 53c7,8xx        PCI     $60    chip, not board. Boards
    by FIC, Chaintech,                (board)    don't include
    Nextor, Gigabyte, etc.                      BIOS, although most
    Mainboards with chip by                non-NCR equipped main
    AMI, ASUS, J-Bond,                    boards have the SDMS
    etc. Common in DEC                    BIOS
    PCI systems)
NCR53c815 (           53c7,8xx        PCI    $100    NCR53c810 plus
    Intel PCISCSIKIT,                    bios
    NCR8150S, etc)
NCR53c825           53c7,8xx        PCI     $120    Wide variant of
                            NCR53c815.  Note that
                            the current Linux
                            driver does not
                            negotiate for wide
                            transfers.
Pro Audio Spectrum 16    pas16        ISA        Sound board w/SCSI
Seagate ST01        seagate        ISA    $20    BIOS only works with
                            some drives
Seagate ST02        seagate        ISA    $40    ST01 w/FDC
Sound Blaster 16 SCSI     aha152x        ISA        Sound board w/SCSI
Western Digital 7000    wd7000        ISA        w/FDC
Trantor T128        t128        ISA
Trantor T128F        t128        ISA        T128 w/FDC and
                            support for high IRQs
Trantor T130B        g_NCR5380    ISA
Ultrastor 14F        ultrastor    ISA        w/FDC
Ultrastor 24F        ultrastor    EISA        w/FDC
Ultrastor 34F        ultrastor    VLB

Notes :
1.  Trantor was recently purchased by Adaptec, and some products are being
    sold under the Adaptec name.

2.  Ultrastor recently filed for Chapter 11 Bankruptcy, so technical
    support is non-existant at this time.

3.  The price for the busmastering NCR53c810 boards is not
    a typo, includes the standard ASPI/CAM driver package for
    DOS, OS/2 and Windows (32 bit access), and other drivers are
    available for free download.

    Some people have had luck with the following companies :


       SW ([e-mail]) [phone] fax [phone]

    As of 23 Dec 1995, their price was $53 on '810 boards.

4.  Adaptec's recent SCSI chips show an unusual sensitivity
    to cabling and termination problems. For this reason,
    I cannot recommend the Adaptec 154x C and CF revisions or the
    2xxx series.

    Note that the reliability problems do not apply to the
    older 154x B revision boards, 174x A revision boards,
    or to my knowledge AIC-6360/AIC-6260 based boards (1505, 1510,
    1520, etc).

    Also, the quality of their technical support has slipped markedly, with
    long delays becoming more common, and their employees being ignorant
    (suggesting there were non-disclosure policies affecting certain
    literature when there were none), and hostile (ie, refusing to pass
    questions on to some one else when they couldn't answer them).

    If users desire handholding, or wish to make a political statement,
    they should take this point into consideration.  Otherwise, the
    Adaptec 152x/1510/1505 are nicer than the other ISA boards in the
    same price range, and there are some excellent deals on used and
    surplus 154x B revision boards and 1742 boards which IMHO outweigh
    the support problems.

5.  All given prices for the DPT controllers are official list prices.
    Street prices should be considerably lower.
    All boards can be upgraded with cache and raid modules, most of the
    boards are also available in Wide and/or Differential versions.

6.  The various NCR boards are not entirely equivallent.  Ie, while
    the ASUS SC200 uses active termination, many other NCR53c810
    boards use passive termination.  Most '825 boards use active
    termination, but some use a ROM for BIOS and others have a
    FLASH ROM.  Most '825 boards have a WIDE external connector,
    WIDE internal connector, and narrow internal connector, although
    a few (ie, CSC's less expensive model) lack the narrow internal
    connector.

Section 9.9 : Summary

    Most ISA, EISA, VESA, and PCI users will probably be served best by a
BusLogic MultiMaster board, due to its performance, features such as active
termination, and Adaptec 1540 compatability.  There are a number of models
available with EISA, ISA, PCI, and VESA local bus interfaces, in single ended
and differential, and 8/16 bit SCSI bus widths.  The most recent Ultra SCSI PCI
models, the BT-948/958/958D, also include Flash ROM for easy firmware updates,
as well as automatic "smart" termination.

    People with PCI systems should consider NCR53c8xx based boards.  These
are bus mastering SCSI controllers, '810s are available quantity one for $53
(ie, cheaper than the Adaptec 1520).  C't magazine benchmarked the boards
as faster than both the Adaptec 2940 and BusLogic BT-946C (under DOS),
and they get reasonable performance under Linux (up to 6M/sec through the
file system ). The disadvantages of these boards versus the BusLogics
are that they aren't Adaptec 1540 compatable, may or may not come with
active termination, you'll need the latest driver revision (standard
in 1.3.5x, also available via anonymous FTP for 1.2.x) to make full use
of the hardware, and are more likely to have problems than with a mailbox
interface board like a BusLogic or DPT.

    Where everything working right on the first try is imperative, a
BusLogic MultiMaster or DPT board is probably optimal due to the
complexity and potential for problems in non-mailbox interface boards like
the NCR53c8xx and Adaptec AIC7xxx .

    People wanting non-PCI SCSI on a limited budget will probably be
happiest finding a surplus or used Adaptec 154x B revision or 174x A
revision, or an Adaptec 1520 clone of some sort (about $80) if they want
new hardware.  These boards offer reasonable throughput and interactive
performance at a modest price.

Section 10 : Assignment of minor numbers

Due to constraints imposed by Linux's use of a sixteen bit dev_t with
only eight bits allocated to the minor number, SCSI disk, tape,
CDROM, and generic minor numbers are assigned dynamically.
iaccording to the following procedure :

    For all SCSI host adapters, from scsi0 through scsiN
            For all SCSI IDs on this bus, from 0 through 7, except for
          this host adapter's ID
                For all logical units, from 0 through max_scsi_luns
          - Probe the bus, target, and LUN combination by
            issuing a TEST UNIT READY command.  If we don't
            think a unit was here, don't probe any more LUNs
            on this bus + SCSI ID.
          - Send an INQUIRY command to determine what we've
            found; including the device type, vendor, model,
            firmware revision, etc.
          - Pass the results of this to a special recognition
            function for each high level driver present (i.e. disk,
            tape, etc).  Attach this device to the next available
            unit for any drivers that are willing to drive this.
            The generic device will attach to all devices.
          - If it was SCSI-I, or in a list of devices known
            not to handle multiple LUNs, don't probe any more
            LUNs on this bus + SCSI ID.
          - If it is a device known to have multiple LUNs, then
            a scan of the full LUN spectrum is forced, overriding
            max_scsi_luns.

There are frequently problems with this approach because if you have a
system where some devices are only present some of the time, then the
minor numbers for a given device will depend upon which devices were
present at boot time.  This can present problem, because rc scripts or
the file /etc/fstab might contain instructions for mounting specific
partitions which fails when the disk appears with a different minor
number.

    This problem has not yet been fully solved.  There is a
program which can be found on tsx-11 that creates a /dev/scsi heirarchy
based upon host number, id and lun.  This is a bit clumsy, but it would
help to alleviate some of the problems.

    A better solution will probably come out of the /proc/scsi pseudo
directory.  This is currently a work in progress, so at present we cannot
say exactly the form of the solution, but at the time of this writing
this appears to be a promising approach for resolving some of these
issues.
EOF