MP 1,1-5,1 Memory slot mac pro 5.1 3.46ghz 12core not working.

[macha-one]

Hi, i am in need of some advice.
I have an issue with memory slot 1 in my mac pro 5.1 3.46 ghz 12 core and Rx580 gpu Running Mojave.
I have six 8gb sticks installed. All 1333 mhz. Slot 1 seems not to be able to see any of the sticks. I tried them all out in different memory slots. All sticks are working. Slots 2345678 are ok. So i am quite certain memory 1 slot is not working properly.
I also have a red light on the motherboard lighting up…..
Still my mac is working without any problems with 40 gb and not using the memory installed in slot 1.
I tried using the stick in slot 3 and then i get 48gb again. But i loose the advantage of triple memory in slots 1,2,3 and 5,6,7.
Could it be better to use slots 234 and 678 to get the advantage of triple memory installed and not use slots 1 and 5?
Of course the best solution would be a fix for slot 1…..
But what would be a solution to fix the slot? I cleaned it with dust off and a toothpick. No result……. I am aiming to install eight 16 gb sticks if the slot can be fixed so any help in this is very much appreciated.
Thanks in advance! Happy holidays🎄

 

[tsialex]

Check the CPU socket pins, you have one or more:

• oxidation on the CPU pads
• oxidation on the CPU socket pins
• bent pin on the socket, use a magnifier glass and look from various angles/different lights

 

[macha-one]

Thnx for your input tsialex!. Much appreciated. i remember you helped me with tips on my way with starting to upgrade my 12 core many years ago. i ll have closer look with a magnifying glass. I understand that what you call the sockets are what I called the memory slots. But where /what are the cpu pads?

 

[tsialex]

I understand that what you call the sockets are what I called the memory slots.

No, it's really the Xeon socket, not the memory slot. There are 1366 pins there, you probably have one that is part of the DIMM 1 circuit that is bent or oxidated.

The memory slot is just a more practical way to connect the CPU to the memory, the signals are routed directly from the DIMM to the CPU, since the memory controller is inside the Xeon CPU.

But where /what are the cpu pads?

Below the Xeon, the golden contacts.

 

[macha-one]

Ok thank you. That clarifies.