Re: PC boot block programming madness

From: Steve Dubrovich (spamtrap_at_crayne.org)
Date: 11/07/04 

Date: Sun, 7 Nov 2004 17:52:37 +0000 (UTC)

spamtrap@crayne.org (KVP) wrote in message news:<9f459d85.0410282251.4d271900@posting.google.com>...
> Florian Liebig <spamtrap@crayne.org> wrote:
> > hello erik!
> > I really do not want to anger you too much but let me have an interruption on
> > your words right now.
> > I do not know if you are going to develop something os-independant like me,
> > but
> > if you are, the things i've told you were right up to the income of your mail
> > and that really pisses me off !!!
> > so these were my theses:
> > 1st) you won't need a starting jump
>
> False, some bioses do check the short jump + nop pair. (bytes 0 and 2)
>
> > 2nd) you won't need a BiosParameterBlock
>
> True, this is only for fat formatted floppies. Other oses don't use it.
> You can just leave it out without problems.
>
> > 3rd) you won't need to worry about 0x1FE significance
>
> False, all pc compatible bioses should check this. Apparently, most machines
> from bigger manufacturers (non asian ones) check this. (Ibm systems tend to
> silently skip the floppy during the boot sequence, when they don't see the
> 0xaa55 flag.)
>
> The only major os that was missing this feature was sco unix, and grub has
> a specific workaround built-in, just to enable this buggy os to boot.
>
I'll have to eat some crow. I've found that the Seagate SCSI ST-01
H.D. Controller's bios does check for 0xAA55 at the end of a floppy's
boot sector. It won't load the sector.

Using a Future Domain SCSI Controller allows the floppy boot w/o the
signature word. There's a difference in the controller bioses,
obviously.

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