The PAT48AN Motherboard
The SIS 486 ISA Motherboard
The SIS486 3-VLBUS Motherboard
I get lots of email concerning other motherboards. I only have manuals for the above three motherboards, and I am definitely not a hardware wizard!
I been told that the The Micro House Technical Library CD is a good source for motherboard info. The only catch is that it's more expensive than a new board!
This website is also a good resource.