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

[Mark Benson]

Hi,

Well... today's been a trying one. I got my Mac PRo 1,1 back last 
weekend and decided, having got Linux 64-bit to run on it and being 
pretty confident it'll at least run OS X 10.11 with some minor coaxing, 
I decided to strip it down as, at the very least, it badly needed cleaning.

While I was at it I bought some Xeon X5355 CPUS (4 cores each at 2.66 
GHz) to try and give it some extra legs. I got 4 because they were quite 
cheap (that's probably not a good sign, I know) and used CPUs are 
sometimes a gamble.

Well I spent the whole day putting the machine back together (having 
removed large parts and cleaned them and let them air out overnight). 
Reassembly was a pig but I got there in the end. I booted it up only to 
find both CPUs overheat almost immediately. Read outs from the on-board 
sensors show the CPUs are idling at 57Cish and rise rapidly on 
application of any stress (leading to Mac OS X beach-balling because 
it's presumably) but the Heatsink Temperatures (taken directly above the 
plate that sits on the CPU) are in the low 30s and don't budge.

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.

The CPU-A heat-sink seems to sit down hard on the top and bottom edge of 
the CPU plate and not in the middle. I did make sure I'd tightened them 
both down as hard as I dared, but it might not have been enough? I 
didn't use any kind of lever, just a small screwdriver and extension bar.

Has anyone ever done this job before, either on a Mac Pro or other 
Socket 771 board? What thermal paste did you use and how much? How tight 
are those bolts supposed to be?

Frustrated. Help appreciated.

-- 

Mark Benson
twitter.com/MDBenson