RE: Using int 13 while BSD is running

From: Jason Dictos (jason.dictos_at_yosemitetech.com)
Date: 03/10/04

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    To: 'Erik Trulsson' <ertr1013@student.uu.se>, Jason Dictos <jason.dictos@yosemitetech.com>
Date: Wed, 10 Mar 2004 09:32:03 -0800

    Point well taken.

    -Jason

    -----Original Message-----
    From: Erik Trulsson [mailto:ertr1013@student.uu.se]
    Sent: Wednesday, March 10, 2004 9:24 AM
    To: Jason Dictos
    Cc: 'Sergey 'DoubleF' Zaharchenko'; Dan Nelson;
    ''freebsd-questions@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@student.uu.se
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