I’ve written up a LinuxBIOS build tutorial for the Gigabyte m57sli-s4.
This tutorial still works off Yinghai Lu’s big MCP55 patch, but a patch from Ed Swierk hit the list today which resolves the last issues for building the m57sli code (if you disable the USB debug code). I’ve tested it – it works fine – so I hope it will be merged into the tree later today or tomorrow. I’ll update the tutorial when that happens.
Remaining issues for the m57sli port are: ethernet MAC address changes between proprietary BIOS and LinuxBIOS (but that might get resolved soon), and no ACPI support yet.