Re: How to restore BIOS-based backup on a UEFI machine

[Tixy <tixy@yxit.co.uk>]

On Thu, 2021-01-14 at 13:45 -0500, The Wanderer wrote:
> On 2021-01-14 at 12:58, Tixy wrote:
> 
> > On Thu, 2021-01-14 at 11:15 -0500, The Wanderer wrote:
> 
> > > Newer-model Intel chipsets specifically prohibit booting to
> > > internal hard drives in "legacy boot" mode.
> > 
> > Surely it isn't the chipset which determines what disk format you can
> > boot from, it's the firmware.
> 
> I'd have thought so too, but the reading I did on this a while back
> (after discovering that booting to MBR-based internal hard drives was
> impossible on the newest computer models at my workplace) led me to
> statements that firmware writers can't support this anymore, because
> Intel's chipset implementation specifically does not let them do it.
> 
> In practice, now that I research this again in depth, not only can I not
> find those statements again, all the reports of this behavior in the
> real world seem to be on Dell computers. I remember finding it stated
> that Dell had no choice in this because of what Intel had done, but I'm
> not finding those again now.
> 
> I *do* find multiple statements that Intel is dropping all BIOS support
> from its UEFI firmwares (including, presumably, those it creates with /
> for its motherboard partners) by sometime in 2020, which has already
> passed; it's possible that that might include this behavior, but I'm not
> finding explicit statements of or reports about that just yet.

That seems more likely, i.e. OEMs using Intel firmware for Intel
chipsets and Intel dropping the Compatibility Support Module (CSM).
And, reading some more, perhaps things are chipset related after all,
if the CSM runs in old 16-bit mode and it can't access all the hardware
it needs.

I don't know enough about this, I would have thought that CSM support
world somehow call out to UEFI to do the actual device work, but after
having passing dealings many years ago with the open source EFI code
(EDK2) it not something I would want to look into. (Me shudders at the
thought :-)

-- 
Tixy