[geeks] Mac Pro 1,1 CPU Upgrade - failure?

[Andrew Jones]

On 12/11/2016 09:09 AM, Mark Benson wrote:
>
>
> This says the thermal junction between the CPU heat spreader and the
> heat-sink is bad. I took it apart, and found CPU-A heatsink wasn't
> totally touching the plate, or at least had made an incomplete junction
> (would explain a lot) but CPU-B looked fine. I redid both the CPU
> heatsink junctions, using bit more arctic silver in case my skimping had
> stopped it working. Reassembled it and... now it's even worse. The CPUs
> are at 57C and the machine crashes within minute of booting.
>

You want to use as little thermal paste as possible.  The coat should be 
so thin it's not visible to the naked eye.

Thermal paste has a better thermal conductivity than air, but it's much 
worse than metal-to-metal contact.  The goal is just to exclude any air 
from defects on the surface.

P.S. don't take the degrees C values too literally.  I don't think those 
thermistors are calibrated against anything.  They're there to detect 
catastrophic rises in temperature to avoid toasting the chip.