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Re: simple message under BIOS/CSM/LEGACY

From: Pascal
Subject: Re: simple message under BIOS/CSM/LEGACY
Date: Wed, 3 Aug 2022 16:11:12 +0200

*this is python biting its tail ;-)*

here is what I plan to test :
leave the protective partition in place (1), mark it as active (2) and
change its first sector to zero (3).

1) its absence seems to be a problem (at least with qemu/ovmf),
2) gdisk does not activate it by default,
3) the MBR and the first sector of the active partition will be confused
and will both have the boot strap loader (BSL eg. the code) to display the

*if the BIOS needs nothing but the 0x55AA signature, it loads MBR and runs
BSL.if the BIOS needs a (table of) partition before loading MBR and handing
over to BSL, it has it.if the BIOS needs an active partition, it has it and
if it loads its PBR instead of MBR, it has it too.*

the only point that seems contentious to me is whether a partition can have
its first sector set to zero ?
does the BIOS check this kind of thing ?

will give feedback...

regards, lacsaP.

Le mar. 2 août 2022 à 23:55, Pascal Hambourg <> a
écrit :

> Le 02/08/2022 à 12:56, Pascal wrote :
> >
> > Gregory(@syslinux) highlights the PBR :
> > *"""Well, I'm still just guessing, but some BIOS systems might execute a
> > PBR (partition boot record) instead of the MBR if one exists and the
> > partition is marked active.
> That sounds horribly broken. Conversely, some BIOS won't boot if no
> partition is marked active in the MBR. Granted, that's equally broken.

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