So I recently bought a second Xeon X5670 and a CPU riser card  for my T5500. I installed it per the service manual, making sure the riser card was properly seated and all the cables were connected, but the system won't post or boot. On the front panel, lights 2,3, and 4 will start blinking and the power light will become amber. According to the service manual, this means control can't be turned over to the BIOS.

I've not done this before, so I'm not sure how to troubleshoot it. Removing the riser card restores normal functionality and the system will boot. I am dealing with second hand parts, so there is some risk of defective parts, but I'm not sure if it might be the 2nd CPU, the riser card, or the memory I've installed. Any pointers would be welcome.

EDIT: I know only certain motherboards will take Westmere Xeons. Will only certain riser cards work with Westmeres? This one's part # is 0F623F.