So the board is stable now. That's great.
Some observations:
1. 'halt' no longer powers the machine off, which it does with the proprietary bios. 'halt -p' does the job though. LinuxBIOS oddity?
2. reboots seem to cause problems sometimes. I'm not sure yet what causes this, but I've had problems with the machine hanging after
ACPI: Unable to locate RSDP
It normally sits there for a few seconds, but I had the machine in such a state that it simply hung at that point.
This may have had something to do with the IPMI card, which I'm experimenting with. I had to unplug the power before this problem went away, a cold restart didn't help. I will do more testing to see if I can pinpoint this.
Thanks for all your help so far! Ward.