[coreboot] Dualbios on GA-MA770-UD3

[Peter Stuge]

Vadim Girlin wrote:
> Please, post any info you have that can help me.

This has been discussed a few times before.

Gigabyte holds a patent for this technology. See
http://www.mail-archive.com/linuxbios@linuxbios.org/msg05929.html
for the link.

The patent describes how the DualBIOS scheme works.

There is a timing circuit and a special handshake. The board starts
up with one chip selected, and if the handshake is performed by the
BIOS before timeout then the system starts normally.

In case of a timeout, the timing circuit resets the board, activates
the second flash chip, and then releases reset to attempt startup
with the new flash chip.

Details of the handshake are not included in the patent, and I expect
them to vary by board.

GA-M57SLI-S4 has pads for the timing circuit, but parts are not
populated. Me and Reinder investigated how the M57SLI board works,
details can be inferred from http://stuge.se/m57sli/

On the M57SLI the timing circuit was drawn quite far away from the
flash chips - with components totally unrelated to the superio - it
was located underneath the battery holder.

I think it will be difficult to learn the handshake details from
looking at the board, and I do believe SerialICE can be helpful here.


//Peter