Hey everyone, You guys have been such a great help in the past I figured I'd ask for your assistance once more! I tried to install two X5660s into a Mac Pro 2009 flashed to 5,1. One CPU works just fine but the moment I try to screw in CPU B the system just boots forever. Eventually a red light turns up and nothing happens. I've tried 3 different CPUs, two of which I can guarantee work. I didn't add washers but I added thermal pads to the bottom sensor array Any ideas? EDIT: More Details. The red light that stays on is OVTMP CPUB. I'm going to check tomorrow for bent pins, if I can't find anything I'm going to give up and go back to the old pocessors. EDIT: Success! I delidded the processors by using the Vise Method (then I shaved off as much of the solder as I could with a razor, thermal pasted, used the little shells that came with the old CPU, installed it) and it worked. Thank you everyone here!