MP 1,1-5,1 cMP 2009 dual CPU - Random shutdowns

costabunny

macrumors demi-goddess
Original poster
May 15, 2008
2,464
58
Weymouth, UK
Hi y’all

My Mac Pro 4.1 dual CPU was a swap for my XBox One S. It was purchased direct from Apple UK by my friend who did the swap. He has had it in his photography studio, and it has done light work over it’s life.

Anyways; first thing I had to do was put a boot disk in it and re-install MacOS. I put a Crucial MX300 series 960Gb into SATA bay 1. I also have a Kingston 120GB in SATA bay 2.

Long story short - got it updated to 5.1 and hubby treated it to a nice little Radeon 560 GPU so I could put Mojave on it. I love it, Mojave/Dark Mode etc.

Anyhows, Once I had finished messing with the OS (installing my utils etc, setting it up my way) I left it running the screen saver. I noted that the screen went off after about 20mins or so. I figured it was sleeping or something. Later when I tried to wake it, I realised that it wasn’t sleeping; it was powered off!

So fired it up and all seemed ok. I added a couple upgrades, namely a pair of X5680 3.33GHz 6-core CPU’s, 6x4GB DDR3-1333 ECC modules to give 24GB in total so that my lovely Mac would last me many years of being my main computer. I keep the PC mostly for games.

Anyways, I have had more sudden, and random shutdows. When it happens, there is no log entries so it has to be hardware. I have tried reseating everything. Noticed a problem in CPU socket A; namely a pin or maybe two out of alignment. Now I must have done this as I am certain I was the first person to remove the CPU’s.

When it works; everything works fine. I can hammer all fans, all 24 threads and the GPU and everything behaves as it should, except that I may get a sudden shutdown. When it shuts down, it refuses to restart without a nice rest! Pressing the power button just gives me two clicks of a relay that I guess is the PSU. I suspect something is heating up, and then triggering a CPU return condition that is causing a emergency shutdown?

The diagnostics in system report passes every boot. Nothing whatsoever in the logs.

I have bought a refurb PSU, and still get the same issue.

I have a new CPU tray coming tomorrow to try it out. If not the CPU Tray (which is my bet); then I shall have to replace the main logic board, which looks like a real pain in my butt.

Has anyone else ever seen this problem? Or am I going to be the one to document it, when I eventually find the culprit. I really want to know exactly why this is happening. As someone with Aspergers it is driving me crazy!

Anyways, sorry for the long post but I do supper from verbal/typing excesses lol
 

Snow Tiger

macrumors 6502a
Dec 18, 2019
854
567
Hi y’all

My Mac Pro 4.1 dual CPU was a swap for my XBox One S. It was purchased direct from Apple UK by my friend who did the swap. He has had it in his photography studio, and it has done light work over it’s life.

Anyways; first thing I had to do was put a boot disk in it and re-install MacOS. I put a Crucial MX300 series 960Gb into SATA bay 1. I also have a Kingston 120GB in SATA bay 2.

Long story short - got it updated to 5.1 and hubby treated it to a nice little Radeon 560 GPU so I could put Mojave on it. I love it, Mojave/Dark Mode etc.

Anyhows, Once I had finished messing with the OS (installing my utils etc, setting it up my way) I left it running the screen saver. I noted that the screen went off after about 20mins or so. I figured it was sleeping or something. Later when I tried to wake it, I realised that it wasn’t sleeping; it was powered off!

So fired it up and all seemed ok. I added a couple upgrades, namely a pair of X5680 3.33GHz 6-core CPU’s, 6x4GB DDR3-1333 ECC modules to give 24GB in total so that my lovely Mac would last me many years of being my main computer. I keep the PC mostly for games.

Anyways, I have had more sudden, and random shutdows. When it happens, there is no log entries so it has to be hardware. I have tried reseating everything. Noticed a problem in CPU socket A; namely a pin or maybe two out of alignment. Now I must have done this as I am certain I was the first person to remove the CPU’s.

When it works; everything works fine. I can hammer all fans, all 24 threads and the GPU and everything behaves as it should, except that I may get a sudden shutdown. When it shuts down, it refuses to restart without a nice rest! Pressing the power button just gives me two clicks of a relay that I guess is the PSU. I suspect something is heating up, and then triggering a CPU return condition that is causing a emergency shutdown?

The diagnostics in system report passes every boot. Nothing whatsoever in the logs.

I have bought a refurb PSU, and still get the same issue.

I have a new CPU tray coming tomorrow to try it out. If not the CPU Tray (which is my bet); then I shall have to replace the main logic board, which looks like a real pain in my butt.

Has anyone else ever seen this problem? Or am I going to be the one to document it, when I eventually find the culprit. I really want to know exactly why this is happening. As someone with Aspergers it is driving me crazy!

Anyways, sorry for the long post but I do supper from verbal/typing excesses lol
Most likely , dust in the PSU ( please clean it with a compressor at 60 PSI and 6 inches away from the hose nozzle ) and failing thermal paste on the Northbridge Controller ( NB ) Chip Heatsink . Maybe also a broken push pin from the same Heatsink . Re-thermal paste the NB controller chip with a fresh coat of Arctic MX4 and verify the two factory push pins are still in good shape .
 

costabunny

macrumors demi-goddess
Original poster
May 15, 2008
2,464
58
Weymouth, UK
Most likely , dust in the PSU ( please clean it with a compressor at 60 PSI and 6 inches away from the hose nozzle ) and failing thermal paste on the Northbridge Controller ( NB ) Chip Heatsink . Maybe also a broken push pin from the same Heatsink . Re-thermal paste the NB controller chip with a fresh coat of Arctic MX4 and verify the two factory push pins are still in good shape .
Thanks for that. As I already tried a refurbed PSU, I think I will have a look at the Northbridge cooler.

I have also just found the Technicians guide for my mac. I have read talk of a diag button which I want to locate and try it both before booting and directly after a shutdown.

I will return...... :)
 

Snow Tiger

macrumors 6502a
Dec 18, 2019
854
567
Thanks for that. As I already tried a refurbed PSU, I think I will have a look at the Northbridge cooler.

I have also just found the Technicians guide for my mac. I have read talk of a diag button which I want to locate and try it both before booting and directly after a shutdown.

I will return...... :)
Unfortunately , you will not learn how to rebuild a NB controller heatsink from that guide . Apple probably considered it a problem too far in the future or rare to immediately worry about . Also unfortunately , all the dual CPU Mac Pro 4,1 and 5,1 have failing NBs these days , so its a prime suspect for System failures .
 
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