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1992-06-15
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adaptec
AHA-1540B/1542B
Addendum
to the
User's Manual
and
Installation Guide
Using Disk Drives Over 1
Gigabyte Under DOS 5
Extended Translation
Adaptec host adapters have always supported the full
range of disk drive sizes under all major operating systems.
As disk drives have recently grown beyond
1 Gigabyte in formatted capacity, they have run up
against the DOS 1024 cylinder limit.
To continue to provide support of all SCSI disk drive
capacities under DOS, Adaptec has introduced
extended translation. This new feature bypasses the
DOS disk capacity limit and supports disk drives up to
8 Gigabytes in size under DOS, providing room for
years of disk drive evolution.
The DOS One Gigabyte Limit
All versions of DOS are limited to 1024 cylinders of capacity
per drive. The standard translation scheme for
SCSI host adapters, using 64 heads and 32 sectors, provides
a maximum accessible capacity of 1 Gigabyte.
To eliminate the 1 Gigabyte limit, Adaptec's new extended
translation feature uses 255 heads and 63 sectors,
extending the disk drive capacity limit under
DOS to 8 Gigabytes.
When to Use Extended Translation
With DOS Version 5 Only
NetWare 386 and the newer versions of UNIX (such as ATT/USL all versions,
SCO v3.2.4 or later, ISC v3.0 or later) do not
share the 1024 cylinder limit of DOS and do not require
extended translation to support large disk
drives. 0S/2 does not currently support extended
PtPHPranslation, but IBM OS/2 v2.0 has support for full capacity with drives
greater than one Gigabyte using HPFS partitions (exception: the boot partition
is limited to one Gigabyte or less). NetWare 386 has full support for drives
greater than a gigabyte with the standard translation scheme.
With Disks Supported by the Host
Adapter BIOS Only
In a system that has only SCSI disk drives, the host
adapter BIOS controls only those drives at SCSI IDs 0
and 1. For systems that have a mix of SCSI and non-
SCSI disk drives, see the section titled Questions and Answers about extended
translation in this addendum.
Drives With Mixed Partitions
Do not use extended translation on drives formatted
with two or more partitions for different operating systems.
Use standard translation. The sum of the DOS
partitions will be less than 1 Gigabyte. Partitions for
UNIX and NetWare can be larger than 1 Gigabyte
when using standard translation.
How to Use Extended Translation
Back Up All Data
Changing translation schemes ,on a disk drive erases
all data on the drive Back up all drives on the SCSI
bus prior to making the change,
CAUTION
If you have already partitioned a large disk drive
with one translation method, conversion to another
method will erase your data. Be sure to back up
your disk drive prior to any change in the transla-
tion method used.
Install Jumper on J6
Install a jumper on pin pair 2 on jumper block J6.
Refer to Figure 2-1 on page 2-2 of the User's Manual or
Default Settings and Reference Diagram in the
Installation Guide for the location of jumper block J6.
Refer to the figure of jumper block J6 on page 2-9 of
the User's Manual or the Installation Guide for the location
of pin pair 2 (Spare 1).
Installation of this jumper enables extended translation
for disk drives controlled by the BIOS exceeding
1 Gigabyte in capacity. Other disk drives are not eligible
for extended translation and will continue to use
standard translation.
Using fdisk
To install a new disk, or to re-partition an existing
disk, use the fdisk DOS utility as you normally would.
The cylinder size increases to 8 MBytes when you enable
extended translation. The size of the partition you
request must therefore be a multiple of 8 MBytes. If
you request a partition size that is not a multiple of 8
MBytes, fdisk will round up to the nearest whole multiple of 8 MBytes.
Load ASW-1410 v3.0a
Load ASW-1410 v3.0a for ASPI support of more than
two disk drives or for non-disk peripheral devices.
ASW-1410 is also often used for compatibility with 386
memory managers. You can upgrade for free to ASPI4DOS.SYS v3.0a by using the
UPGRADE program on the Adaptec BBS.
To protect your data, extended translation is not downward
compatible with earlier versions of software drivers.
If you intend to use ASPI-compatible software
with your host adapter for support of more than two
disk drives or for non-disk devices, install ASW-1410
v3.0a (or later).
Questions and Answers About
Extended Translation
What Happens if I enable extended translation
with SCSI drives that have less than 1 Gigabyte in
capacity?
Drives handled by the BIOS will use extended translation
provided they are over 1 Gigabyte in formatted capacity.
Drives with less than 1 Gigabyte of formatted
capacity will use standard translation regardless of
whether extended translation is enabled. Drives handled
by the disk driver ASPIDISK.SYS will continue to use
standard translation and not be capable of DOS partitions
over 1 Gigabyte.
How do I know which hard disk drives the BIOS
controls?
Your system allows up to two hard disk drives under
BIOS control; first SCSI ID O, then SCSI ID 1. Your
system may have either two non-SCSI, one non-SCSI
and one SCSI, or two SCSI hard disk drives.
What if I use older versions of software drivers
with extended translation enabled?
To protect your data, the host adapter will lock out out
driver that does not identify itself as capable of extended
translation. If you need to use software that is
not compatible with extended translation, do not enable
extended translation.
Adaptec's ASW-1410 v3.0a (and later) is the appropriate
ASPI manager software to use with extended translation
enabled.