Strange things with my hard drive

[Kerry Hoath]

Some boards don
't like talking to drives over 28gb or so. but I doubt this is
your problem. 
The reality is that you can only get at  8.4gb of disk in chs mode
i.e. standard int13. It works like this:
int 13 function call 2 read sector.
registers:
ah=2 al=number of sectors.
es:bx points at area of memory to receive data.
dh=head 1-255
dl=drive letter: 0 for a: 1 for b: 80 for hard disk 1 81 for hard disk 2.
cl=cylinder 0-255
ch=sector to start reading from 0-63 top 2 bits of ch are top 2 bits of cylinder.
This gives us a sector range of 1-63 and
a cylinder range of 0-1023.
1024 cylinders 255 heads and 63 sectors per track gives you a maximum legacy
capacity of 8.4gb or so.
To read beyond that you need to use LBA (Linear block addressing)
and to use that in bios you must use the phoenix int13 extentions.
Dos can't use int 13 extentions or at least
versions up to 6.22 can't.
Dos also can't boot beyond 2gb on a disk due to a calculation bug in the default dos boot sector.
Newer lilo versions i.e. 20 and up can use int13 extentions.
Older versions can not. If your bios has int13 extentions most things after 1994 do you can place your linux partitions wherever assuming ide.
Scsi it all depends on the onboard scsi bios.
Lilo 20 and up can boot just about anything on a new machine. lilo <20 or
a bad bios and you'll need to keep linux /boot partition below the first 8.4gb so
the bios can load the kernel or stick a floppy in the drive.
Yes I have no life but perhapse this may clear up some of the 
incomplete/missinformation on this topic floating around.
Once the kernel is booted linux's ide driver uses lba when available and can access
up to 4 terabytes since kernel 1.1.51 or so.
Getting the kernel loaded still requires co-operation from the bios and your boot loader of choice
lilo grub silo nt boot loader system commander etc.

Regards, Kerry.
On Tue, Feb 26, 2002 at 12:14:56AM +0100, Victor Tsaran wrote:
> Well, I don't know what the biggest size the motherboard supports, but I've
> been running my 20GB hard disk with no probs before on this same
> motherboard.
> Vic
> 
> 
> 
> 
> 
> 
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-- 
Kerry Hoath:  kerry at gotss.net kerry at gotss.eu.org or  kerry at gotss.spice.net.au