[coreboot] Dualbios on GA-MA770-UD3

Vadim Girlin vadimgirlin at gmail.com
Fri Apr 9 08:12:05 CEST 2010


Sorry for my bad english.

I'm going to try coreboot on Gigabyte GA-MA770-UD3.
It's AMD 770 (RX780 / SB700).

I've prepared the image for it based on code for mahogany fam10 with
some modifications.

I've tried it with simnow using the configuration close to mine as much
as possible - it even boots with my native BIOS. And it boots with
coreboot image.

My motherboard supports hardware dual bios - with two chips on it.
I'm going to try flashing backup chip and boot from it. It seems to be
possible - I've tested it (flashing at least). Chips on this board could
be switched by changing bit 0 at undocumented register EF on LDN 7 of
IT8720. I can use slightly patched flashrom for accessing any chip I
want without any problems. And this is tested many times.

My idea is to use backup chip for debugging - that always keeps my
chance to reboot from main bios chip. And removes the need for
desoldering etc.

But the problems are when I'm trying to boot - and I expected them. It
seems that after warm reboot it is trying to boot from selected chip as
I want, but reboots againg in a second. AFAIK there is some hardware
watchdog on these dualbios motherboards. There are many possibilities -
northbridge, southbridge, superio.

My main question is - is anybody working on it or may be have some info
on it. I definitely will find the way to turn the watchdog off but may
be somebody already did that?

And second problem is that original bios is checking second chip - and
trying to recover it by flashing the bios from main chip on reboot?
rewriting coreboot. AFAICS this could be solved by including some
signatures etc. It seems to be easy to find out. May be someone is
working on this?

BTW I can send the patch for flashrom - but I think that with
information I mentioned above somebody could make it much better than my
ugly hack. I hope the regs should be the same for all latest Gigabyte
MBs using IT8720/18

Please, post any info you have that can help me.

Best regards,

Vadim Girlin

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