Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!udel!mmdf
From: Peter_Van_Epp@cc.sfu.ca
Newsgroups: comp.os.minix
Subject: Re: Minix & Hardcards
Message-ID: <38601@nigel.ee.udel.edu>
Date: 10 Dec 90 08:02:54 GMT
Sender: mmdf@ee.udel.edu
Lines: 36

The way I always figure out the geometry of the disk (and I just got a new
200 M drive and a 386 machine!) is to let the disk bios tell me from DOS.
All you need is a 5 line program under debug (assuming of course that you
have MSDOS!) that looks like this
a 100
mov ah,8
mov dl,80
int 13
nop
nop
 
then do a g=100,106 and when the breakpoint is hit the carry flag should be
clear (indicating success) and the drive parameters are as follows:
ch = max usable cylinder (low 8 bits)
cl = bits 7 and 6 = high 2 bits of max cyl
     bits 5 - 0 = max sector #
dh = max usable head
dl = number of drives.
es:di = address of disk param table (which you don't care about).
This should get you the info you need to feed to fdisk.
Example for my 200m drive:
 
ch = CE 
cl = DC
dh = 0E
dl =1
 
so there are 3CE (or 974) tracks (top 2 bits of cl and all of ch) 
              1C (or 28) sectors per track (from cl bottom 5 bits) 
       and    0E (or 14) as the last usable head (from dh). This  is a little
              confusing because that is the last usable head and they start at
              0 so there are actually 15 heads!
given the above the fdisk command looks like this:
fdisk -h15 -s28 /dev/hd0
and voila all falls into place.
Hope this helps!