SOLVED Mac Pro 5.1 CPU/Memory/Logic Board problems

[yiannisspy]

Hi folks,

I am having hardware issues with my Mac Pro 5.1 (single CPU, upgraded from 4.1) which prevent me from using OpenCore and upgrading from Catalina.

I have upgraded the CPU to an Intel Xeon X5690.
I have also upgraded the RAM to 4x 16GB 64GB DDR3 ECC RAM.

Now the problems:
1. Only 48GB of memory are recognized. From switching the DIMMs around I know that none of them are defective. This points to a CPU/Logic Board issues I suspect. A red led remains lit on the logic board next to the DIMMs. When I remove the last 2 DIMMs the red light disappears and the 32GB are recognized .

2. The EFI loader of OpenCore refuses to boot due to a kernel panic like below:
mp_kdp_enter() timed-out on cpu 2, NMI-ing
mp_kdp_enter() NMI pending on cpus: 0 4 5
mp_kdp_enter() timed-out during locked wait after NMI;expected 8 acks but received 6 after 15506108 loops in 1329999830 ticks
panic(cpu 2 caller 0xffffff801a21f51b): "IPI timeout, unresponsive CPU bitmap: 0x10, NMIPI

NOTE: This happens even if I run with 32GB (so without the red light on the logic board).

I have tried re-sitting the CPU and tightening the CPU fan etc. Nothing seems to make a difference. I have tried all combinations with the memory DIMMs, but as I mentioned the kernel panic occurs even if I run on 32GB.

My question is:
Is there a way to know whether this is a CPU issue or a logic board issue? I am willing to replace either because I use this machine for work, but would like to avoid buying both if possible.

Many thanks,
Yiannis

 

[yiannisspy]

In case somebody else stumbles upon this issue, I have made progress and below is a quick breakdown.

It turns out there were two separate issues. The malfunctioning DIMM slot issue remains, but the kernel panic issue went away and I was able to move on with the OS upgrade. Strangely after all this time-consuming effort what fixed it was 3 NVRAM resets. The newly installed RAM (albeit only 48GBs of it) was correctly recognized as 1333MHz while before the Mac only saw 1066MHz. This was probably a hint that could have saved me some time but I am really happy with the outcome regardless.

TLDR; No hardware changes needed, 3 NVRAM resets fixed the machine.

Greetings,
Yiannis