193
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4.6.1 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 GB 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-7896 SCSI controllers. This feature supports disk drives of
up to 8 GB capacity under DOS. The section Extended BIOS Translation for DOS Drives > 1 GB
explains how to change the setting of this option. Most operating systems leave this option
disabled.
4.6.2 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, gives a maximum capacity of 1
GB.
To eliminate the 1-GB limit, Adaptec’s extended translation feature uses 255 heads and 63 sectors,
extending the disk drive capacity limit under DOS to 8 GB.
