Extended Translation (Using Dos 5.0; The Dos 1 Gbyte Limit; When To Use Extended Translation; With Dos V 5.0 Only - Adaptec AHA-2740W User Manual

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Extended Translation (Using DOS 5.0)

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 GByte in formatted capacity, they have run
up against the DOS 1024 cylinder limit.
To continue its support for all SCSI disk drive capacities under DOS,
Adaptec has introduced an extended translation scheme for the
AHA-2740W/2742W/2744W. This new feature bypasses the DOS
disk capacity limit and supports disk drives up to 8 GBytes in size
under DOS, providing room for years of disk drive evolution. To
enable this feature, refer to BIOS Configuration on page 3-12.

The DOS 1 GByte Limit

All versions of DOS are limited to 1024 cylinders per drive. The stan-
dard translation scheme for SCSI host adapters, using 64 heads and
32 sectors, provides a maximum accessible capacity of 1 GByte.
To eliminate the 1 GByte limit, Adaptec's new extended translation
feature uses 255 heads and 63 sectors, extending the disk drive
capacity limit under DOS to 8 GBytes.
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 translation method used.

When to Use Extended Translation

With DOS V 5.0 Only

NetWare 386 and the newer versions of UNIX do not share the 1024
cylinder limit of DOS and do not require extended translation to
support large disk drives.
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AHA-2740W/2742W/2744W User's Guide
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Current Date: 8/3/94
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Disk Drives Over 1 GByte
Page: D-3
ECN Date: 8/9/94
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