Extended BIOS translation (worth disabling?)

[Peter Holzer]

On Thu, Feb 05, 1998 at 10:39:20AM -0500, Reinhold J. Gerharz wrote:
> At 16:10 02/05/1998 +0100, Peter Holzer wrote:
> 
>         ...
> 
> >Yup. For some reason Linux fdisk (like DOS fdisk) only lets you start
> >partitions at cylinder boundaries.

> This is probably to make the partitions compatible with LILO as well
> as DOS. LILO's limitation is that it uses BIOS calls to actually load
> the kernel, therefore inheriting the BIOS limitations. The advantage
> of this is maximum and immediate compatibility with any disk drive
> supported by the BIOS.

The BIOS handles arbitrary partition boundaries fine (all it gets are
"read n sectors starting at cyl a, head b, sector c" requests. It
doesn't even know about partitions). MS-DOS doesn't, but AFAIR it starts
partitions on head 1 (instead head 0) of a cylinder, so either Linux
fdisk cannot create DOS compatible partitions or it already has some
special code for them.

Looking at the partition table of my disk, it looks like fdisk puts the
start of the first partition and all the logical partitions at head 1:

Nr AF  Hd Sec  Cyl  Hd Sec  Cyl   Start    Size ID
 1 00   1   1    0 254  63   75      63 1220877 83
 2 00   0   1   76 254  63   83 1220940  128520 82
 3 00   0   1   84 254  63  147 1349460 1028160 83
 4 00   0   1  148 254  63  262 2377620 1847475 05
 5 00   1   1  148 254  63  211      63 1028097 83
 6 00   1   1  212 254  63  212      63   16002 83
 7 00   1   1  213 254  63  262      63  803187 83

This is almost certainly for the sake of FAT-Filesystems, because most
other filesystems would happily start at Head 0, Sector 2 of a cylinder.

I don't know what happens if I try to install DOS on my partition 3. 

	hp

-- 
   _  | Peter J. Holzer             | If I were God, or better yet
|_|_) | Sysadmin WSR                | Linus, I would ...
| |   | hjp at wsr.ac.at               |     -- Bill Davidsen
__/   | http://wsrx.wsr.ac.at/~hjp/ |        (davidsen at tmr.com)
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