BIOS support for disks larger than 1024 cylinders

SCO OpenServer Handbook
Chapter 18, Adding hard disks

Disks with more than 1024 cylinders are supported with the following restrictions:

The disk controller must support disks with more than 1024 cylinders.
If the disk is configured as the primary hard disk, the boot filesystem (/stand) for SCO OpenServer software and the bootable disk partition for any other operating system must lie within the first 1024 cylinders. This is because the BIOS in ROM cannot access information that lies beyond the 1024th cylinder. If the boot filesystem falls outside the first 1024 cylinders, an error message will be displayed by boot(HW) as follows:
```
   Error: request outside range of BIOS (1023 cylinders)
```

You can use the rest of the disk for swap space, the root filesystem and additional filesystems.

The BIOS on some IDE, most EIDE, and all SCSI disk controllers allows remapping or translation of large disks so that they appear to have less than 1024 cylinders. For example, the extended BIOS for the Adaptec 1542, 1742, and 274x controllers allows 2GB SCSI disks to be mapped as 255 heads, 63 sectors and 255 cylinders.

If you are upgrading your system rather than performing a new installation, the root filesystem must fit within 1024 cylinders because there is no separate boot filesystem in this case.