Last year I upgraded the processors in my dual processor Mac Pro from the standard 2.4GHz (4 cores each) to a pair of X5675 3.06GHz (6 core) processors.
There are photos of this job here:
https://forums.macrumors.com/showthread.php?p=19955322#post19955322
My previous 2.8GHz single processor 2010 Mac Pro had been sitting in the corner for ages, so it was time that I sold it. Before I bought the dual processor Mac Pro I had already bought a W3680 processor and 32Gb RAM to use in that Mac. I found a buyer, who wants the processor and RAM.
I started by removing the processor and RAM tray.
The heat sink is attached with five bolts, which are removed with a 3mm allen key. There are four bolts around the processor and the fifth one is on the far left.
I used ArctiClean to clean off the old heatsink thermal paste, but as flowrider previously covered, regular isopropyl alcohol will do the same job.
Once I had removed the majority of the thermal paste I finished cleaning it off with a micro-fibre cloth.
I then removed the old 2.8GHz processor.
I put the replacement W3680 processor in place and put some new thermal paste on.
I had previously used a cotton stick to spread the thermal paste around, but this time I wanted to try something plastic. The only thing that I could find was the plastic stalk of a cotton stick. I cut the end off so that I could use it to roll around and spread the paste.
I had applied too much thermal paste, so rolling the plastic stalk around was good for removing some of it.
Then I was ready to put the heatsink back on. In this photo it looks like there’s too much paste but it was actually a thin layer.
I put the heat sink back on, which involved carefully pushing down on each bolt with the allen key to get the end of each bolt to reach the threads on the board.
I put in the two spare 16Gb RAM sticks that I had (Samsung M393B2G70BH0-YH9). Much to my delight, the Mac Pro started up properly the first time.
Just like last time, I was nervous about doing this. But it was all done and finished so quickly that it was an anti-climax. I could do the whole job again in a few minutes if I had to.
For anyone who’s considered this but hasn’t done so yet… do it!