xeon 5100 series matched pair required?

So I have a tyan tempest i5000XL with a single xeon 5150 processor. I just purchased another 5150 for the empty socket, and, guess what, it didn't work when i popped it in. Just some beeps (the tyan manual isn't very helpful on this). Both processors work fine when alone on the board, but when either is placed in the second socket, neither works.

My question: what factors could be causing this? Do the processors need to be "matched" in any way? Both are "Intel Confidential" processors - could they be different generations (I could clean off the thermal compound and post some serial numbers if that would be helpful). Would you suspect a motherboard flaw?

Any lead would be appreciated.

Thanks!

From what I know, they do have to be "matched" in the sense that they must have the same sSpec Number, which would at least mean they have to be the same stepping. I have two xeon 2.8 CPU's in a server that have the same sSpec but very different serial numbers and the system works fine.

thanks for the help!

they do have different stepping





damn