Adaptec/MS-DOS Support for Drives Greater than 1 GB (99290)
This article was previously published under Q99290
The Adaptec manual is somewhat misleading when it states that MS-DOS
imposes a 1G limit on storage drives. MS-DOS is limited to 1024 cylinders,
but it allows more heads and sectors per track (255 heads and 63 sectors)
than does Adaptec (64 heads and 32 sectors). Adaptec adopted the SCSI
standard in order to surpass 1G, but a drive is not going to run unless
MS-DOS supports it.
To support drives greater than 1G, you need to enable extended BIOS
translation in EISA CONFIG, and Adaptec's 9/17/92 bid works only when
the drive isn't the boot device.
Problems can occur when it IS the boot device. When setting up a drive's
geometry, DISK.TSD determines if it is the boot drive. If it is, use the
ROM chain entry (BIOS related) to set the geometry because the machine has
to boot from the ROM. This is probably where the Adaptec problem arises:
the bid is reporting the correct values but the BIOS information has to
come from the adapter, which appears to be setting values incorrectly.
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