MP 1,1-5,1 Mac Pro 4,1 -> 5,1 shuts down after a few minutes

[chrisb42]

Hi all, my trusty 4,1 (flashed to 5,1) all of a sudden just shut down without being under load and wouldn't properly start up anymore. After it cooled off, it will boot again, but within 5 minutes or so before it just shuts down again.

I read the threads about the temperature issues and cleaned and replaced the thermal paste both for the CPU (I have a single CPU tray, running one X5675) and the Northbridge (which was completely baked and hard). However, it still shuts down after a few minutes, even though the temps from what I could gather in iStat were fine (and certainly lower than before).

Is my CPU tray broken? I assume the CPU is fine, otherwise it wouldn't even work for the initial 5 minutes, correct? What part of the tray would cause this behavior all of a sudden? Nothing had changed hard- or software wise in quite a while; I'm running Mojave with OpenCore, booting from an NVMe SSD, and this configuration has been stable for quite a while now.

I assume it is still somewhat heat-related, as it did happen on one of those hot days we had recently; currently running with a borrowed 2 CPU tray from a different 4,1 and that works perfectly fine, despite showing much higher temps in some areas (no thermal paste replaced there yet), so I know the rest of the system works fine.

Thanks for pointing me in the right direction.

 

[tsialex]

Could be a short, usually happens with one the PWM MOSFETS, the Qxxx components near the CPU socket. Look for bubbles/burn in signs.

 

[chrisb42]

If it's anything like this, I should start looking for a replacement, because I wouldn't be able to fix that…

 

[m1maverick]

If you've diagnosed the problem to the CPU tray my recommendation is to just buy a replacement. Here's a 4,1 single CPU tray for $35 OBO + ~$18 shipping:

Apple A1289 Mac Pro 820-2482-A CPU Processor Tray Intel Xeon W3530 2.80GHz QC​

Another for $41.87 OBO + $16.00 shipping:

Apple 820-2482-A Memory Board 2.8GHz Q. Core Xeon W3530 w/ Heatsink 16GB OF RAM​

Or step up to a dual CPU tray for $79.99 + ~$29.00 shipping:

Apple 630-9402 Mac Pro 4,1 A1289 2009 CPU Tray 2x Intel CPU 2.26GHz​

 

[chrisb42]

Yeah, luckily parts are available for relatively little money. I don't really need dual CPUs for what I do. Also, how much more is the power draw of dual CPUs vs a single one?

Having said that, I'm contemplating getting a "real" 5,1 with dual CPU lots of memory that's offered locally for $250.

 

[chrisb42]

To answer my own question regarding power draw, there is an official document available here:

Mac Pro power consumption and thermal output (BTU/h) information - Apple Support

Learn about the power consumption and thermal output of Mac Pro computers.

support.apple.com

I think I'll stick with getting a new single-CPU tray for my machine.

Thanks for the information and links to the parts!

 

[YZFNYC]

Have you replaced the plastic clips on your North Bridge chip heat sink? If not check it. If it's that go to ace hardware and get a couple of small bolts with nuts and replace.