Mac Pro 2009/4,1 Dual Socket - no chime, no boot with both CPUs

dangerweenie

macrumors newbie
Original poster
Sep 17, 2018
2
0
My 4,1 / 2009 unmodified dual proc Mac Pro was having intermittent crashes (every *other* boot, it would randomly freeze). I took the CPU tray out and discovered a wiggly northbridge heatsink that needed to be refastened to the board. Taking off CPU-A to get to it, I noticed the thermal paste was pretty dessicated and flakey (about ten years old now), so I decided to take both CPUs off, clean and repaste both of them (as well as the Northbridge heatsink).



Assembling everything again, the Mac Pro would not boot up (no chime). I spent the next several hours following the technician's manual minimal configuration (removed *everything* from the computer - HDDs, Graphics card, RAM, processors), progressively powering up and checking DIAG LEDs, and going for that chime.



The most progress I've been able to make (in terms of actually getting to a chime), is with *only* CPU-A installed.-



I've actually tested both CPUs in the CPU-A socket, and have been able to get to a chime (minimal RAM, no HDD, no GFX card).



The moment I put a CPU in socket B, I can only get a solid light, no chime. Case fans spin up in all cases.



DIAG LED with CPU-A installed (no graphics card), EFI OK, 5V OK, and GFX card OK.



DIAG LED with CPU-A & CPU-B installed (still no graphics card), EFI OK, 5V OK, GFX card blinking.



There are no red error lights on either CPU socket (unless I boot with only CPU-A (and CPU socket B empty)), in which case the CPU-B red light is on.



Booting up with NO RAM (only CPUs):



CPU-A only - front panel blinking white power light (not enough RAM).
CPU-A & CPU-B - front panel white power light is solid, no chime.



I've spent quite a bit of time carefully reading people's issues with this model (solid light, no chime), it seems to be more common with those who are trying to upgrade 4,1 processors.



I am unable to get to a chime, or even power on, without the CPU tray installed - the technician manual is unclear on this - does anyone know if the backplane should be able to at least turn on even without CPU tray installed?



I've removed and reinstalled coin cell battery, and reset SMC / System via shorting the jumper connections on the backplane board.



Possibilities I am currently thinking about-



1.Short in CPU-B socket involving power (hence no CPU-B error light or CPU-B overheat light, and also inability to chime).
2.Something wrong with CPU-B cooling fan / heat sink temperature sensor? Would this completely fail a hardware self-test? I would assume that it would still boot and then the CPU-B OVERHEAT light would go on.
3.Pins in CPU-B socket pushed down too far due to overtightening? Wouldn't there be a CPU FAILURE light on (like when I try to boot with nothing in the socket), if this were the case? Visual inspection of the sockets look OK.

Does anyone know if there is any way to check the cpu board / socket-B for hardware issues?



I'm deeply grateful to anyone who can shed some light on what might be going on. I'm happy to append some pictures of the sockets / CPUs, motherboard, anything that coule potentially help.



Thanks in advance.



Matt
 

ActionableMango

macrumors G3
Sep 21, 2010
9,514
6,772
This is pure speculation, but my guess is that prior to your cleanup you had a part-time back plane board or CPU tray hardware failure due to some physical reason (such as a "barely-there" short or crack due to thermal expansion). The problem was intermittent due to varying conditions like vibration and/or heat expansion. Then the physical stresses and movement while doing your cleanup caused the existing partial/intermittent failure to complete its failure.

If you have another 4,1/5,1 you could swap in the known good board or tray for troubleshooting to see what works and what doesn't. That would enable you to identify the failed part and get a replacement. If you don't, I'm not sure what to say other than you could take it into an Apple certified repair shop and have them diagnose. Based on other posts here, I suspect that they would be able to narrow it down to either backplane board or CPU tray failure fairly quickly.

It would be interesting to see your logs from the pre-cleanup intermittent crash period, in case there is something like Kernal Panic text that can be examined. That might be illuminating as to the problem.
 
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h9826790

macrumors G5
Apr 3, 2014
14,148
6,785
Hong Kong
My 4,1 / 2009 unmodified dual proc Mac Pro was having intermittent crashes (every *other* boot, it would randomly freeze). I took the CPU tray out and discovered a wiggly northbridge heatsink that needed to be refastened to the board. Taking off CPU-A to get to it, I noticed the thermal paste was pretty dessicated and flakey (about ten years old now), so I decided to take both CPUs off, clean and repaste both of them (as well as the Northbridge heatsink).



Assembling everything again, the Mac Pro would not boot up (no chime). I spent the next several hours following the technician's manual minimal configuration (removed *everything* from the computer - HDDs, Graphics card, RAM, processors), progressively powering up and checking DIAG LEDs, and going for that chime.



The most progress I've been able to make (in terms of actually getting to a chime), is with *only* CPU-A installed.-



I've actually tested both CPUs in the CPU-A socket, and have been able to get to a chime (minimal RAM, no HDD, no GFX card).



The moment I put a CPU in socket B, I can only get a solid light, no chime. Case fans spin up in all cases.



DIAG LED with CPU-A installed (no graphics card), EFI OK, 5V OK, and GFX card OK.



DIAG LED with CPU-A & CPU-B installed (still no graphics card), EFI OK, 5V OK, GFX card blinking.



There are no red error lights on either CPU socket (unless I boot with only CPU-A (and CPU socket B empty)), in which case the CPU-B red light is on.



Booting up with NO RAM (only CPUs):



CPU-A only - front panel blinking white power light (not enough RAM).
CPU-A & CPU-B - front panel white power light is solid, no chime.



I've spent quite a bit of time carefully reading people's issues with this model (solid light, no chime), it seems to be more common with those who are trying to upgrade 4,1 processors.



I am unable to get to a chime, or even power on, without the CPU tray installed - the technician manual is unclear on this - does anyone know if the backplane should be able to at least turn on even without CPU tray installed?



I've removed and reinstalled coin cell battery, and reset SMC / System via shorting the jumper connections on the backplane board.



Possibilities I am currently thinking about-



1.Short in CPU-B socket involving power (hence no CPU-B error light or CPU-B overheat light, and also inability to chime).
2.Something wrong with CPU-B cooling fan / heat sink temperature sensor? Would this completely fail a hardware self-test? I would assume that it would still boot and then the CPU-B OVERHEAT light would go on.
3.Pins in CPU-B socket pushed down too far due to overtightening? Wouldn't there be a CPU FAILURE light on (like when I try to boot with nothing in the socket), if this were the case? Visual inspection of the sockets look OK.

Does anyone know if there is any way to check the cpu board / socket-B for hardware issues?



I'm deeply grateful to anyone who can shed some light on what might be going on. I'm happy to append some pictures of the sockets / CPUs, motherboard, anything that coule potentially help.



Thanks in advance.



Matt
Did you try swap CPU yet? Both CPU can boot in socket A?
 
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