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  Linux SCSI HOWTO
  Drew Eckhardt, [e-mail]
  v2.15, 20 March 1995

  This HOWTO covers the Linux SCSI subsystem, as implemented in Linux
  kernel revision 1.1.74 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.

  1.  Introduction

  1.1.  License

  Noncommercial redistributions of a verbatim copy in any medium
  physical or electronic are permitted without express permission of the
  author.  Translations are similarly permitted without express
  permission if they includes a notice on who translated it.

  Commercial redistribution is allowed and encouraged, provided that the
  author is notified of any such distributions and given opportunity to
  to provide a more up-to-date version.

  Short quotes may be used without prior consent by the author.
  Derivative work and partial distributions of the SCSI-HOWTO must
  include either a verbatim copy of this file or make a verbatim copy of
  this file available. If the latter is the case, a pointer to the
  verbatim copy must be stated at a clearly visible place.

  In short, we wish to promote dissemination of this information through
  as many channels as possible. However, we do wish to retain copyright
  on the HOWTO documents, to be notified of any plans to redistribute
  the HOWTOs to insure that outdated versions don't spread too far, and
  for ALL the information provided in the HOWTOS to be disseminated. If
  you have questions on the Linux documentation project, please contact
  Matt Welsh, the Linux HOWTO coordinator, at [e-mail].
  Questions regarding this document itself should be addressed to Drew
  Eckhardt, [e-mail].


  1.2.  Important Note

  IMPORTANT:

  BUG REPORTS WHICH FAIL TO FOLLOW THE PROCEDURE OUTLINED IN SECTION 2
  WILL BE IGNORED.

  For additional information, you may wish to join the SCSI channel of
  the Linux activists list - mail to linux-activists-
  [e-mail].  with the line


  X-Mn-Admin: join SCSI



  in the header, as well as the Linux SCSI list by mailing
  [e-mail] with the line


  subscribe linux-scsi



  in the text.


  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.



  2.  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.


  2.1.  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
  <ftp://tsx-11.mit.edu/pub/linux/ALPHA/scsi> for more information about
  active termination.


  2.2.  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 image 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



       boot:




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



       boot: ?

       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



       boot: 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"





  2.3.  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.


  2.4.  A SCSI device shows up at all possible LUNs

  The device has buggy firmware.

  As an interim solution, 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.


  2.5.  You get sense errors when you know the devices are error free

  Sometimes this is caused by bad cables or impropper termination.

  See ``'': General Flakiness


  2.6.  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.


  2.7.  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

  wildcards ``should'' work - ie







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







  ``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 3: 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





  2.8.  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.


  2.9.  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




  Regardless of whether 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





  2.10.  LUNS other than 0 don't work

  This is often a problem with SCSI-> MFM, RLL, ESDI, SMD, and similar
  bridge boards.

  At some point, we came to the conclusion that many SCSI-I devices were
  extremely broken, and added the following 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;
  ______________________________________________________________________



  to scan_scsis() in drivers/scsi/scsi.c.  If you delete this code, your
  old devices should be detected correctly if you have not used the
  max_scsi_luns kernel command line option, or the NO_MULTI_LUN compile
  time define.



  3.  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.


  3.1.  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 Ctrl-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.


  3.2.  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.


  4.  Hosts


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


  4.1.  Supported and Unsupported Hardware

  Drivers in the distribution kernel :

  Adaptec 152x, Adaptec 154x (including clones from Bustek and DTC 329x
  boards), Adaptec 174x, Adaptec 274x/284x/2940, 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.

  Alpha drivers: Richoh GSI-8

  Many of the ALPHA drivers are available via anonymous FTP from
  <ftp://tsx-11.mit.edu:/pub/linux/ALPHA/scsi>

  Drivers that are being developed, but aren't publically available yet,
  and modifications needed to make existing drivers compatable with
  other boards: DPT PM2001

  Announcements WILL be made when drivers are available for public alpha
  testing.  Until then, please don't use up the developers' valuable
  time with mail asking for release dates, etc.


  o  NCR53c8x0/7x0

  o  A NCR53c8xx driver has been developed, and with modifications
     ranging from minor to severe should support these chips

  o  NCR53c720 - detection changes, initializaion changes, modification
     of the assembler to use the 720's register mapping

  o  NCR53c710 - detection changes, initialization changes, modification
     of assembler, modification of the NCR code to use fatal interrupts
     or GPIO generated non fatal interrupts for command completion.

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

  o  NCR53c9x family

  o  Qlogic

  SCSI hosts that will not work :

  o  All parallel-> SCSI adapters

  o  Rancho SCSI boards

  o  and Grass Roots SCSI boards.

  SCSI hosts that will NEVER work:


  o  Non Adaptec compatable DTC boards (including the 3270 and 3280).

     Aquiring programming information requires a non-disclosure
     agreement with DTC.  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 an 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.





  4.1.1.  Multiple host adapters

  With some host adapters (see ``'': 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


  1. Ultrastor

  2. Adaptec 151x/152x

  3. Buslogic

  4. Adaptec 154x

  5. Adaptec 174x

  6. Future Domain 16x0

  7. Always IN2000

  8. Generic NCR5380

  9. PAS16

  10.
     Seagate

  11.
     Trantor T128/T130

  12.
     NCR53c8xx

  13.
     EATA-DMA

  14.
     WD7000

  15.
     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.


  4.2.  Common Problems


  4.2.1.  SCSI timeouts

  Make sure interrupts are enabled correctly, and there are no IRQ, DMA,
  or address conflicts with other boards.


  4.2.2.  Failure of autoprobe routines on boards that rely on

  BIOS for autoprobe.

  If your SCSI adapter is one of the following :


  o  Adaptec 152x

  o  Adaptec 151x

  o  Adaptec AIC-6260

  o  Adaptec AIC-6360

  o  Future Domain 1680

  o  Future Domain TMC-950

  o  Future Domain TMC-8xx

  o  Trantor T128

  o  Trantor T128F

  o  Trantor T228F

  o  Seagate ST01

  o  Seagate ST02

  o  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 ``''.


  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.


  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.


  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
  <ftp://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 diffs
  files and patch is beyond the scope of this document.

  See also ``'': Configuring and building the kernel


  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 'Always 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 #include 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 ``'': Configuring and building the kernel


  4.3.  AIC 6260/6360 based products (Standard) Adaptec 152x, 151x,
  Sound Blaster 16 SCSI, SCSI Pro, Gigabyte, and other



  4.3.1.  Supported Configurations :


     BIOS addresses:
        0xd8000, 0xdc000, 0xd0000, 0xd4000, 0xc8000, 0xcc000, 0xe0 000,
        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 board
        s, including the Adaptec 1510, and Sound Blaster16 SCSI must use
        a kernel comma nd line or compile time override.


     Autoprobe Override:
        None

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


     kernel command line
        aha152x=< PORTBASE> ,< IRQ> ,< SCSI-ID> , < RECONNECT>
        Usually, SCSI-ID will be 7 and RECONNECT non-zero. To force d
        etection at 0x340, IRQ 11, at SCSI-ID 7, allowing
        disconnect/reconnect, you wou ld use the following command line
        option :



          aha152x=0x340,11,7,1





     Antiquity Problems, fix by upgrading:
        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 scsiid of AIC-6260 (0-7) (default 7)

           RECONNECT:
              override target dis-/reconnection/multiple

           outstanding command:
              set to non-zero to enable, 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
  4.4.  Adaptec 154x, AMI FastDisk VLB, Buslogic, 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:
        works with all supported configurations, does not require an
        installed BIOS.



     Autoprobe override:
        none


     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 and EISA
        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

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

        o  BIOS support for > 2 drives

        o  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 ``'': Common
           Problems, and Section ``'': 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 # 2 and # 3 and Section ``'': Common
           Problems, and Section ``'': 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 # 2 and # 3 and Section ``'': Common
           Problems, Section ``'': General Flakiness and Section
           ``'':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.

  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.


  4.6.  Adaptec 274x, 284x, 294x (Standard)

  Newer revisions may be available at
  <ftp://ftp.cpsc.ucalgary.ca/pub/systems/linux/aha274x/aha274x-pre-
  alpha.tar .gz>

  Supported Configurations:

     274x:

        EISA Slots:
           1-12

        IRQs:
           ALL

        IO:
           port mapped, bus master

     284x:

        Ports:
           All

        IRQs:
           All

        DMA Channels:
           All


     294x
        PCI


     Note:
        BIOS MUST be enabled

     Note:
        The B channel on 2742AT boards is ignored.



  4.7.  Always IN2000  (ALPHA)

  ALPHA driver available at
  <ftp://tsx-11.mit.edu/pub/linux/ALPHA/SCSI/in2000>.  The driver is
  in2000.tar.z, bootable kernel zImage

     Port:
        0x100, 0x110, 0x200, 0x220

     IRQs:
        10, 11, 14, 15

     DMA:
        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.


  4.8.  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

        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://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.

              a. 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.

              b. 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.


  4.9.  p Future Domain 16x0 with TMC-1800, TMC-18C30, TMC-18C50, or
  TMC-36C70 chi


     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:
           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.


  4.10.  Generic NCR5380 / T130B


     Supported and Unsupported Configurations:

        Ports:
           all

        IRQs:
           all

        DMA:
           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:

        o  ncr5380=port,irq

        o  ncr5380=port,irq,dma

        o  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



             ncr53480=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.


  4.11.  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 ``'':System Hangs When Swapping

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

     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.

           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.

           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 occur when using an S3928P, X11, and the NCR chip at
           the same time.

           There are hardware bugs in at least some S3928P chip.  Don't
           do this.

        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. 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.


        o  Intel P90 boards require revision 1.00.04.AX1


  4.12.  Seagate ST0x/Future Domain TMC-8xx/TMC-9xx


     Supported and Unsupported Configurations :

        Base addresses:
           0xc8000, 0xca000, 0xcc000, 0xce000, 0xdc000, 0xde000

        IRQs:
           3, 5

        DMA:
           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

           a. Write byte to data register, data register is asserted to
              bus

           b. time_remaining = 12us

           c. wait while time_remaining > 0 and REQ is not asserted

           d. if time_remaining > 0, assert ACK

           e. wait while time remaining > 0  and REQ is asserted

           f. deassert ACK

           The problem was encountered in slow devices that do the com-
           mand 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 multi-
           ple 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.

  4.12.1.  Common Problems


  4.12.1.1.  Command Timeouts

  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.


  4.12.1.2.  Some Devices Don't Work

  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).


  4.12.1.3.  Future Domain does not work

  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.


  4.12.1.4.  HDIO_REQ or HDIO_GETGEO failed

  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 ``'': Partitioning


  4.12.1.5.  Fdisk fails

  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 ``'': Partitioning


  4.12.1.6.  Used to work but now it doesn't

  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 : 0x4
  0));
  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 : 0x4
  0));
  sti()
  ______________________________________________________________________


  may fix your problem.


  4.12.2.  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.

  4.13.  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:
           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:

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

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

        o  PARITY - enable parity checking.  Not supported

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


        o  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.


        o  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.


  4.14.  Trantor T128/T128F/T228


     Supported and Unsupported Configurations:

        Base addresses:
           0xcc000, 00xc8000, 0xdc000, 0xd8000

        IRQs:

        o  none, 3, 5, 7 (all boards)

        o  10, 12, 14, 15 (T128F only)

        DMA:
           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.


  4.15.  Ultrastor 14f (ISA), 24f (EISA), 34f (VLB)


     Supported Configurations:

        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 to

           a. 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.

           b. 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.


  4.16.  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''


  5.  Disks

  This section gives information that is specific to disk drives.


  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, and MO
  drives work.

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


  5.2.  Common Problems



  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 ``'': Disk Geometry and Partitioning for a n explanation.


  5.2.2.  You are unable to partition ``/dev/hd*''


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

  See Section ``'': Device files, and Section ``'', Disk Geometry and
  Partitioning for the correct device names and partitioning procedure.


  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.



  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.





  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 ``'': Partitioning


  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().


  5.2.7.  System Hangs When Swapping

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


  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




  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 prima
  ry partitions, minors 5 < = (minor % 16) < = 15 any extended
  partitions.

  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 disk minor
  numbers are assigned dynamically starting with the lowest SCSI
  HOST/ID/LUN.

  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

                 Device        type      major     minor
                 /dev/sda      block       8         0
                 /dev/sda1     block       8         1
                 /dev/sda2     block       8         2
                 /dev/sda3     block       8         3
                 etc.



  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 ``'': 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.


  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.


  6.  CDROMs

  This section gives information that is specific to cdrom drives.


  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.


  6.2.  Common Problems

  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.


  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.


  6.2.3.  Unable to play audio.


  The programs Workman or xcdplayer will do this for you.


  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  <ftp://tsx-11.mit.edu/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.


  6.3.  Device Files


  SCSI CDROMs use major 11.

  Minors are allocated dynamically (See Section 4: Disks, Subsection
  4.3: 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} ie

  /dev/sr0 /dev/sr1

  etc.


  7.  Tapes


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


  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 :

  o  Archive Viper QIC drives, including the 150M and 525M models

  o  Exabyte 8mm drives

  o  Wangtek 5150S drives

  o  Wangdat DAT drives


  7.2.  Common Problems



  7.2.1.  Tape drive not recognized at boot time.


  Try booting with a tape in the drive.


  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.



  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





  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

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


  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.


  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.


  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/nrst{digit} for non-rewinding
  devices /dev/rst{digit} for rewinding devices


  8.  Generic


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


  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.


  8.2.  Common Problems


  None :-).


  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.


  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.





  9.1.  Transfer types


  The biggest factor affecting performance (in terms of throughput and
  interactive response time during SCSI I/O) is going to be the transfer
  type used.




  9.1.1.  Pure Polled handshaking.


  A pure polled I/O board will use the CPU to handle all of the SCSI
  processing, including the REQ/ACK

  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/IO.  Slow CDROMs which don't
  disconnect/reconnect will kill interactive performance with these
  boards.

  Not recommended.


  9.1.2.  Interlocked Polled handshaking


  Boards using interlocked polled I/O are essentially the same as pure
  polled I/O boards, only the SCSI REQ/ACK signals 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 re 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 CDROMs 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.


  9.1.3.  FIFO Polled


  Boards using FIFO polled I/O put a small (typically 8K) 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.


  9.1.4.  Slave DMA


  Drivers for boards using slave DMA program the PC's 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
  limit DROM drives).

  Acceptable for slow CDROM drives, tapes, etc.


  9.1.5.  Busmastering DMA


  These boards are intelligent.  Drivers for these boards throw a SCSI
  command, the destination target and lun, and where the data should end
  upin 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).


  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 headrate, through the filesystem, reading and writing, to 75%
  and 100% respectively using an Adaptec 1540 series board.


  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, and must be modified to take advantage of the features
  present on newer chips.


  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.


  9.4.1.  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.



  9.4.2.  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.


  9.4.3.  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.


  9.4.4.  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 and poor return policies
        EISA ISA VESA PCI


     Performance, and typical hobbiest installations
        PCI EISA VESA ISA

  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.


  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 very important
  if you are mixing devices of different speeds, like a tape drive 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, for example.  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.


  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.


  9.7.  Driver feature comparison


  Driver feature comparison (supported chips are listed in parenthesis)


  Driver                       Transfer mode          Simultaneous Commands         SG         >1
                                                            total/LUN             Limit
  aha152x                      FIFO(8k) Polled                1s/1s                255s
  (AIC6260,
  AIC6360)
  aha1542                      Busmastering DMA               8s/1s                 16         Y
  aha1740                      Busmastering DMA                32s                  16
  aha274x                      Busmastering DMA               4s/1s                255s        Y
  buslogic                     Busmastering DMA                 Y               64s, 8196h
  eata dma                     Busmastering DMA              64s/16s               64s         Y
  fdomain                      FIFO(8k) Polled                 1s                  64s
  TMC1800 except TMC18c30
  TMC18c30, with 2k FIFO
  TMC18c50,
  TMC36c70
  in2000*                      FIFO(2k) Polled                 1s                  255s
  g NCR5380                    Pure Polled                   16s/2s                255s         Y
  (NCR5380,
  NCR53c80,
  NCR5381,
  NCR53c400)
  gsi8*                        Slave DMA                     16s/2s                255s
  (NCR5380)
  PAS16                        Pure Polled or                16s/2s                255s        Y
  (NCR5380)                    Interlocked Polled
  (fails on some systems!)
  seagate                      Interlocked Polled              1s                  255s        N
  wd7000                       Busmastering DMA                8s                   1
  t128                         Interlocked Polled              16s                 255s        Y
  (NCR5380)
  ultrastor                    Busmastering DMA                 Y
  53c7,8xx                     Busmastering DMA               1s/1s                255s        Y
  (NCR53c810)


  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.


  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 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
  Always IN2000        in2000       ISA
  Buslogic 445S        aha1542,     VLB      $250      FAST SCSI-II, active
  buslogic                                             termination, w/FDC
  Buslogic 747S        aha1542      EISA               FAST SCSI-II, active
  buslogic                                             termination, w/FDC
  Buslogic 946S        buslogic     PCI                FAST SCSI-II, active
                                                       termination.
  DPT PM2011           eata dma     ISA                FAST SCSI-II
  DPT PM2012A          eata dma     EISA               FAST SCSI-II
  DPT PM2012B          eata dma     EISA               FAST SCSI-II
  DPT PM2021           eata dma     ISA      $245      FAST SCSI-II
  DPT PM2022           eata dma     EISA     $449      FAST SCSI-II
                                                       active termination
  DPT PM2024           eata dma     PCI      $395      FAST SCSI-II
                                                       active termination
  DPT PM2122           eata dma     EISA     $595      FAST SCSI-II
                                                       active termination
  DPT PM2124           eata dma     PCI      $595      FAST SCSI-II
                                                       active termination
  DPT PM2322           eata dma     EISA               FAST SCSI-II
                                                       active termination
  DPT PM3021           eata dma     ISA      $1595     FAST SCSI-II
                                                       multichannel
                                                       raid/simm sockets
                                                       active termination
  DPT PM3122           eata dma     EISA     $1795     FAST SCSI-II
                                                       multichannel/raid
                                                       active termination




  DPT PM3222                  eata dma      EISA     $1795    FAST SCSI-II
                                                              multichannel
                                                              raid/simm sockets
                                                              active termination
  DPT PM3224                  eata dma      PCI      $1995    FAST SCSI-II
                                                              multichannel
                                                              raid/simm sockets
                                                              active termination
  DPT DTC 3                   aha1542       EISA              Although it should work,
                                                              due to documentation
                                                              release polcies, DTC
                                                              hardware is unsupported
  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       $70     +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      $115     NCR53c810 plus
  Intel PCISCSIKIT,                                           bios
  NCR8150S, etc)
  NCR53c825                   53c7,8xx      PCI               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      IOS 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. Various Buslogic boards other than the 545S, 445S, 747S, and 946S
     _should_ work,  although to my knowledge have not been tried.

  4. The $70 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.

     If you can't find one at that price, try Technoland at
     1-800-292-4500 or 1-408-992-0888 if you live in California,
     InteliSys at [phone], Superpower 1 [phone], SW
     ([e-mail]) 214-907-0871 fax [phone]

     Insight Electronics at 1-609-985-5556 stocks NCR8150S '815 boards
     for $115 if you don't have a NCR SDMS BIOS in your main ROM.

  5. 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.

     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 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.

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


  9.9.  Summary

  Most ISA, EISA, and VESA users will probably be served best by a
  Buslogic 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.

  People with PCI systems should consider NCR53c810 based boards.  These
  are bus mastering SCSI controllers, available in Q1 for about $70 (ie,
  cheaper than the Adaptec 1520) with larger quantities being cheaper
  (I've seen $62 in Q20).  In addition to being the cheapest PCI SCSI
  boards, the NCR boards were also benchmarked as faster than the
  Adaptec 2940 and Buslogic BT-946, and demonstrate excellent
  performance under Linux (up to 4M/sec through the file system )
  inspite of the performance optomizations being disabled in the current
  driver.  The disadvantages of these boards versus the Buslogics are
  that they aren't Adaptec 1540 compatable, don't come with active
  termination, and to my knowledge are only supported under DOS+Windows,
  OS/2, Windows NT, SCO, NeXTstep, and Free BSD.  Currently, the Linux
  driver appears quite stable on most systems (We've moved several
  gigabytes of data to NCR based devices with no problems), surprisingly
  fast (I've seen 4M/sec through the filesystem) and will eventually
  become more featureful.  On the downside, the current Linux driver
  implementation doesn't support disconnect/reconnect, so you will be
  unable to access your SCSI disks if rewinding,retensioning,etc. SCSI
  tapes at the same time.

  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.