rap@la.excelan.com (Robert A. Pease) (04/06/91)
The News Manager) Nntp-Posting-Host: la Reply-To: rap@la.UUCP (Robert A. Pease) Organization: Novell -- San Jose, Ca. Date: Thu, 4 Apr 1991 23:08:24 GMT I just looked at the BIOS reference and confirmed that the values for cylinders, heads and sectors are limited to the following ranges; Cylinders = 0 - 1023 Heads = 0 - 15 Sectors = 0 - 31 If I do my math right, this means that there are a total of 16384 sectors that the BIOS can address (1024 * 16 * 32 = 16384). At 512 Kb per sector, the maximum size HDU that the BIOS can get to is 262 Mb. Now I know that you can put 300 Mb or 600 Mb hard disks on your computer, but how does this work as far as addressability at the BIOS level? rap. ----------------------------------------------------------------------- Robert A. Pease, Novell Inc. Internet: rap@novell.COM
dj@bragi.ctron.com (DJ Delorie) (04/07/91)
In article <1991Apr4.230824.23481@novell.com> rap@la.excelan.com (Robert A. Pease) writes: >Cylinders = 0 - 1023 >Heads = 0 - 15 >Sectors = 0 - 31 > >If I do my math right, this means that there are a total of 16384 >sectors that the BIOS can address (1024 * 16 * 32 = 16384). At 512 Kb >per sector, the maximum size HDU that the BIOS can get to is 262 Mb. The IBM BIOS Technical Reference Manual does not put such a limit on the number of sectors, although the hard drive card may, allowing 8 bits (0-255). Same for heads, which get 6 bits (0-63). Combined, you get 24 bits of sector addressing, for a total of 8 Gb per HDU. Most ESDI and SCSI cards work this way. DJ dj@ctron.com