For detailed information how to build LinuxBIOS itself for a given platform, see http://www.openbios.org/LinuxBIOS-AMD64.pdf
Just what I was after.
The SIS6x0 is not yet supported by the LinuxBIOS v2 tree yet. Which means you cannot replace your motherboard bios with LinuxBIOS on those systems.
Fiddle sticks. That was exactly what I wanted to do. Interestingly enough, the board has a w83627hf on it.
I am not sure what I can do to help get SiS6x0 into v2 but if there is anything, do not hesitate to ask.
Many thanks