Subject: Re: Exactly what does the 1024 cyl limit break?
To: Frank van der Linden <>
From: Matthias Drochner <>
List: port-i386
Date: 12/01/1997 20:34:52
Excerpts from netbsd: 1-Dec-97 Re: Exactly what does the 1.. Joel (517*)

> Presumably the code required to address a drive directly in LBA is too
> large to fit in the bootblock.

You speak about direct hardware access?
Even if it would fit, who would write a driver for
every (IDE/SCSI/fibrechannel) adapter?

> What about the extended int13h functions?
> Does the NetBSD bootblock support those yet?

No, not yet.
It would make sense if NetBSD has the whole disk.
If it doesn't, you still have the problem that the MBR code
or the boot selector must be able to access at least the
first NetBSD track.

> hat would surely enable the
> kernel to be booted from beyond the 504Mb limit.

Assuming that a BIOS which can int13 extensions is
also capable of CHS translation, it is an 8G limit.

There are things to improve in the bootsectors, in
particular they should use the LBA information in
the partition table to get their first 15 sectors. (to become
independant of different BIOS translations)
Unfortunately, nobody had the time so far.

best regards