Installing new CPU(s) in a MacPro 5,1

My old, dead, Mac Pro had a 6-core X5680 Xeon at 3.33 GHz. The “new” one came with dual 6-core X5650 2.66 GHz processors. Things have gotten so cheap, I picked up a pair of X5675s (3.06 GHz 6-core, the fastest processors Apple shipped in a dual processor Mac Pro 5,1 configuration) on eBay for $19 with free shipping. So now I had to install them. (I haven’t installed a processor since the days of the Socket 370. (Edit: I’d only installed one processor, an i5-3570K in a Hackintosh I built in 2011. Forgot about that...)) (Also edit: I looked up the TDP for these processors; the X5675s are 95W, while the X5860s and higher are 130W, so 70W additional in a dual processor setup. Stuck with the 3.06s because I was worried about the additional heat. Stick with what Apple did stock...)

 

My exhaustive 5 minutes of Google searching found several videos that came close to being a full guide, but nothing comprehensive, so I figured I’d write out my experience here. The results were awesome, my single processor score in Geekbench 5 is back to 627. (That’s up from 562 with the 2.66 GHz chips, and the same score I had with the 3.33 GHz! (Probably due to Turbo Boost Technology).) The multi-core score jumped from 3271 (single X5680) to 5791 (dual X5650s) to 6421 (dual X5675s). Cinebench scores were ... Well, the multicore of 506 is just shy of the 509 put on the board by the 8 core Apple M1, and comfortably higher than the 14 core (20 thread) 12th generation Intel Core i7-1280p (433). Single core, bottom of the list of 10, at 36 coming in well behind the next lowest, the 16 core / 32 thread AMD Ryzen Threadripper 1950X (49). The M1 scored 112, while the 12th gen i7-1280P came in at 74.

YouTube videos consulted in this process: 

• Mac Pro 5,1 CPU Upgrade - glosses over the actual CPU installation, but a good look at removing / reinstalling the heat sinks.
• Mac pro 5,1 in 2023 - part 2: upgrading the CPU! Half the video spent vacuuming dust off the CPU tray, but does a good job showing the removal of the CPU, applying thermal paste, etc., but skips over some critical information regarding orientating the CPU in the LGA 1366 socket.
• BEGINNERS GUIDE: How To Apply CPU Thermal Paste
• Best Way to Apply Thermal Paste? Does it Even Matter? (tl;dw: Not really. All the methods of applying paste ended up within a degree or two of each other.)
  

Things I needed:

• Long 3mm hex key ($5)
• ARCTIC MX-4 thermal paste ($7)
• ArctiClean 60ML Kit (30ml ArctiClean1+30ml ArctiClean2) & Microfiber (7" X 6") Cleaning Cloth ($11) (I had this left over from my GPU repaste)

Everything works. Watching the temperature readings from Stats during a CPU benchmark shows the temperature hovering in the 130°F range, exactly where it should be. Huzzah.

 

Step one: Remove the heatsink(s) with the 3mm tool.

The old thermal paste was crusty!

I removed the old thermal paste residue from the heatsink with ArctiClean 1.

The lever to release the CPU in this picture is along the edge next to and parallel with the RAM.

The lever, released, and the old Xeon is now loose.

Make a note of where the triangle in the corner is (pin 1 of the CPU).

Insert the new CPU with the same orientation.

After securing the CPU I prepared the surface with ArctiClean2.

Added a small blob of MX-4 thermal paste, and then reattach the heat sink with the 3mm tool. Watch the fan connector.

Repeat for the other CPU, if applicable. This gives a better view of the lever that locks the CPU into the socket.

Ready to replace this CPU. Note the fan connector for the heatsink, the oval to the right of the socket.

A clean Xeon ready for thermal paste.

Thermal paste applied, ready for the heat sink.