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Appendix ADisk Drives Over 1 GigabyteExtended Translation (Using DOS 5)Adaptec host adapters have always supported the full range ofdisk drive sizes under all major operating systems. As disk driveshave 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 capacitiesunder DOS, Adaptec has introduced extended translation for theAHA-1740A/1742A/1744. This new feature bypasses the DOS diskcapacity limit and supports disk drives up to 8 Gigabytes in sizeunder DOS, providing room for years of disk drive evolution.The DOS 1 Gigabyte LimitAll versions of DOS are limited to 1024 cylinders of capacity perdrive. The standard translation scheme for SCSI host adapters,using 64 heads and 32 sectors, provides a maximum accessiblecapacity of 1 Gigabyte.To eliminate the 1 Gigabyte limit, Adaptec’s new extended trans-lation feature uses 255 heads and 63 sectors, extending the diskdrive capacity limit under DOS to 8 Gigabytes.A-1