I have a Mac Pro "Eight Core" 2.26 (2009/Nehalem) that I was running with dual X5690 (3.46GHz/6-core/12MB/130W) processors for the last couple years (yes, I've got the 2010 firmware hack on it). Been running fantastic, but I needed to do swap some hardware around and so ended up needing to take these processors out and put some older processors (that were from another actual 2010 Mac Pro; 2.66 GHz 6 Core Xeon X5650 x2).
After the transplant was completed I fired it up and immediately got a light on the right side of CPUA:
I held the power button in and immediately turned it off. This light then lit ("OVTMP CPUA"):
I figured something must be up with the heatsink as it seemed as though the screws for the 2009 heatsinks ratcheted down tightly and immediately instead of having some give that would indicate that it was in contact with the CPU (lidded CPU btw). Made me figure that perhaps the heatsink was not pressing down the CPUA processor enough. I also recalled that the previous processor that was in here may have been SLIGHTLY taller.
I then took the heatsink back off and put about .5 to .75 mm of copper cut to size for the Xeon lid and used thermal paste again to make up for this possible spacing issue. I repeated this for CPUB. The heatsink seemed to ratchet down better this time as I could feel some pressure being applied and the torque didn't stop immediately as before and thus i could torque it down a bit.
After doing this, I unfortunately found that the same error lights were emitted - no change.
I also went ahead got some additional feedback from the DIAG LED button:
I'm not really sure what to do at this point. Should I add thicker copper to make the heatsinks apply greater pressure to these Xeon processors?
I believe Intel has pretty good heat protection for these processors, so I don't believe the processor would be "burned out" at this point, right?
Further, would resetting the motherboard by removing the battery and / or pressing the reset button beside the battery (above the 1st PCIe slot / behind the GPU) help at all?
Any other ideas aside from buying a new processor?