Chapter 7 - SCSISelect Configuration Utility 7-23
7.4 Disk Drives Over 1 Gbyte

7.4.1 Extended Translation

Adaptec SCSI controllers have always supported the full range of disk drive
capacities 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
included an extended translation scheme for the AIC-7880 SCSI controllers. This
feature supports disk drives of up to 8 GBytes capacity under DOS. Extended
BIOS Translation for DOS Drives > 1 GByte in this chapter explains how to change
the setting of this option in the SCSISelect utility. Most operating systems will
leave this option Disabled.

7.4.2 The DOS 1 GByte Limit

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