Mac Pro 4,1 No boot/chime


macrumors newbie
Original poster
Jul 23, 2016
I have two Mac Pro 4,1's that I got free from work. One is my main machine and works great (SSD upgrades, Video cards, USB 3.0). The other does not boot or chime. ame specs. Something on the CPU tray is faulty. I've done the following:

Swap CPU tray from Working computer (A) to B and it booted up/chimed. I even swapped out the ram from B to A to make sure that the Ram was not the culprit. B's tray mounted in A's computer does not boot/chime

I've looked around and it seems that the CPU may have come unseated or an issue with the thermal paste? How should I go about testing the bad tray to diagnose?


macrumors regular
Sep 17, 2011
Download technicians manual for 2009 Mac Pro and follow troubleshooting.
Unless someone fiddled with heatsinks there's no way a cpu can just unseat itself.

People always talk about northbridge heatsink coming loose. I would think this would cause machine to shut off when hot, not prevent a boot.

Sounds like something terminal wrong with logicboard.
Last edited:


macrumors G3
Sep 21, 2010
I agree with Leon. The Service Manual has good troubleshooting procedures in it.

The chime occurs after a successful POST, so something is not passing that test.


macrumors G5
Apr 3, 2014
Hong Kong
Sounds like the tray is just dead (e.g. the Northbridge chip is burned).

You may take the tray to some good electronic repair shop and ask them to check if the tray’s component is working.

But if that’s expensive, I think buy a new tray is easier.


macrumors 6502
Dec 6, 2015
Deep South
Check out my recent journey after having a similar problem. Although my cMP is dual CPU, some of the problem solving may give you some ideas on what to do. The first thing I'd do is hold down the power-on button until you hear a chime, then let go, then press the power-on button again and see if that starts it up.

cMP 2009 CPU tray issue
  • Like
Reactions: Frank DiMaulo

Frank DiMaulo

macrumors newbie
Apr 17, 2018
New York
Thank you JedNZ. Your journey prompted me to take off CPU B and see what would happen. Turns out that I was finally able to boot with CPU A only so I reinstalled CPU B and tightened down on the heat sink and it all came back to life. Turns out that heatsink B got too loose and the intermittent connection of CPU B flipped out the MP. I had gotten another backplane board but my original one turned out to be fine.
  • Like
Reactions: JedNZ and howiest