Hi,
I've tried Harald Gutman's ACPI patch for gigabyte m57sli and I can successfully boot Linux with it (straight from flash, 2MB), and, as a bonus, the proprietary NVIDIA driver for X works too with full glx acceleration, hurray!
There are still some errors in dmesg regarding ACPI, though, which is probably why the powernow cpu frequency scaling doesn't work yet. Most notably the FACP checksum is incorrect.
For some strange reason, the ethernet device is 'renamed' to eth1, eth0 doesn't work.
I've attached the output of dmesg.