Adaptec AHA-2742T User Manual - Page 102

Extended Translation Using DOS 5.0, The DOS 1 Gigabyte Limit

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D 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-2740 Series of host adapters. 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 Configure BIOS and SCSI Device in Chapter 3. The DOS 1 Gigabyte Limit All versions of DOS are limited to 1024 cylinders per drive. The standard 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 backup your disk drive prior to any change in the translation method used. Adaptec AHA-2740 Series User's Manual Stock Number: 510381-00 / Rev. C (Page D-3) Print Spec Number: 491709-00 Rev C Current Date: 9/1/93 ECN Date: 9/14/93 D-3

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D
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-2740 Series of host adapters. 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
Configure BIOS and
SCSI Device
in Chapter 3.
The DOS 1 Gigabyte Limit
All versions of DOS are limited to 1024 cylinders per drive. The
standard 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 transla-
tion 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 backup your disk drive prior to any
change in the translation method used.
Adaptec AHA-2740 Series User’s Manual
Stock Number:
510381-00
/
Rev. C
(Page D-3)
Print Spec Number:
491709-00 Rev C
Current Date:
9/1/93
ECN Date:
9/14/93
D-3