[coreboot] Dualbios on GA-MA770-UD3

[xdrudis]

On Sat, Apr 24, 2010 at 08:26:45PM +0200, Patrick Georgi wrote:
> Am 24.04.2010 19:43, schrieb xdrudis:

> They might just use a watchdog:
> - BIOS 1 sets a flag
> - BIOS 1 configures the watchdog to trigger when it's not touched within
> 2 seconds (or whatever). watchdog would reboot the system then
> - BIOS 1 jumps in BIOS 2
> - BIOS 2 does whatever it needs to do to consider itself "safe"
> - Meanwhile, BIOS 2 touches the watchdog every so often
> - BIOS 2 deactivates the watchdog
> 
> In this scenario, coreboot would have to know how to tell the watchdog
> to reset its countdown, and how to disable the watchdog, to safely use
> the Dual BIOS feature.
> 

Ok. I'm rereading the link Gigabyte gave me, which does not explain enough 
or I don't understand it enough, but it might be this scenario you explain

http://www.gigabyte.com.tw/FileList/NewTech/2006_motherboard_newtech/article_04_bios_explained.htm

(the URL says 2006 but it was given to me in a mail in early March 2010) 

I've noticed they say it reboots before running the other BIOS, it's not just
a jump. How would that work ? would it be some flag in CMOS ? 
This is better, I guess in that it gives both BIOSes the same initial state.

It also says the original BIOS checks both BIOS copies, but I guess it doesn't
matter since it will only run if coreboot fails, and then you have to reflash it
anyway.

> The feature supposedly shouldn't just guard against non-Gigabyte images,
> but against issues with their own images, too - and those would have the
> right signature, and thus would pass any such test.
>
> I'd be really amazed if they'd add another chip (that actually costs
> money) and then only implement an incomplete protection scheme with it.
>

Ok. It makes sense. Thank you for explaining.