Using int 13 while BSD is running
Jason Dictos
jason.dictos at yosemitetech.com
Wed Mar 10 09:28:57 PST 2004
Point well taken.
-Jason
-----Original Message-----
From: Erik Trulsson [mailto:ertr1013 at student.uu.se]
Sent: Wednesday, March 10, 2004 9:24 AM
To: Jason Dictos
Cc: 'Sergey 'DoubleF' Zaharchenko'; Dan Nelson;
''freebsd-questions at freebsd.org' '
Subject: Re: Using int 13 while BSD is running
On Wed, Mar 10, 2004 at 08:49:17AM -0800, Jason Dictos wrote:
>
>
> > To Jason: take care not to *write* anything to the disk via int 13h.
> > I still don't think I understand why you are using FreeBSD for this
> specific purpose. Why if you just >spend time escaping from the OS?
>
> We actually _like_ protected mode, it allows us to be more flexible
> and our code doesn't have to be bastardized with 16 dos compilers ;).
> However in dos we have garanteed hard drive support via int13 (Well
> almost garanteed, but if an os can boot of the computer, we can access
> the disk), and I'm looking for the same sorta garantee in BSD. People
> will be using this with raid controllers, scsi hard disks, and ide
> drives (Server recovery), so there will be many times when the
> hardware running the hd requires specific support, which BSD may or
> may not have, point is we dont' want to manage that.
>
> Make sense?
Just because you can boot from the disk does not mean that the BIOS can read
the whole disk.
As an example I have an old computer running FreeBSD with a 1GB disk.
The BIOS in this computer cannot handle disks larger than 512MB (which was a
quite common limitation in older BIOSs). I can however boot from this disk
since all the files needed for booting reside below the 512MB mark. Once I
have booted FreeBSD I can access the whole disk precisely because FreeBSD
does *not* use the BIOS, but use its own routines.
--
<Insert your favourite quote here.>
Erik Trulsson
ertr1013 at student.uu.se
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