Mac Pro 6,1 - 1 RAM DIMM not detected


macrumors newbie
Original poster
May 6, 2018
I recently bought a refurbished Mac Pro 6,1, with 32GB of ram in all 4 slots. After a month, one of my DIMMs is not being detected, leaving me with only 24GB. Can anyone tell me what approach I should take to troubleshoot this? I am new to Macs (but highly technical) and I am hoping someone out there has experience with this kind of thing?


macrumors 6502
Dec 14, 2016
New Orleans, USA
Still under warranty? Don't even crack the case. Return it. Anything you do, they may say it's broken because you touched it.

On a hardware level, the 6,1 Mac Pro is an Intel Xeon workstation crammed inside a shiny trash can. It's a strangely-shaped Intel PC. Each slot is its own memory channel back to the CPU.

Three possibilities:
1. DIMM died. Swap DIMMS, see if all DIMMs work.
2. Slot died. Swap DIMMS among slots, see all slots work.
3. CPU isn't making good contact in socket, so one of the memory channels isn't functional. I wouldn't touch that one. Warranty void if you try to access CPU.
Last edited:


macrumors Core
Feb 9, 2008
Does System Profiler tell you which slot is not detected? Just swap that RAM stick into another working slot and see if it works. Then put a working RAM stick from another slot into the one that is not being detected to see if the slot works.


macrumors newbie
Original poster
May 6, 2018
Ok: here is how I fixed it.

1. My RAM slot #3 was not detected.
2. I opened the case and removed and re-seated slog #3 and rebooted machine
3. After doing that, slot #1 was not not recognized.
4. I opened the case and removed and re-seated ALL 4 DIMMS
5. When I restarted machine it is now fixed and back to normal.

Thanks for your help guys.