So I ended up going with the ASRock mobo. I have only 4 DIMMs to use right now. More are on the way, so eventually all 8 DIMM slots will be filled.

But until then, I will be using only the 4. All the other dual CPU mobos I have seen, say 2 go into the slots around each CPU. It can vary, either two slots next to each other, or alternating slots. But always 2 for each CPU.

This mobo says to put all 4 around just the #1 CPU, even when both CPUs are populated. Can this possibly be right? Check out page 20 of the manual.

https://dl.dropboxusercontent.com/u/...2C612%20WS.pdf

It seems to contradict their own block diagram on page 14, which implies that the DIMM sockets around CPU#1 are all for CPU#1, not shared.

Can page 20 possibly be right?