FYI: Memory Slot bad out-of-box | 2020 iMac 27inch Retina 5K 3.8 GHz 8-Core Intel Core i7

Apr 2, 2021
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Just an FYI in case others come across this. I ordered 4 matched 32GB sticks from OWC. The original 2-4GB sticks were in slots 2 and 4. While trying to troubleshoot this with OWC, we determined that all 4 sticks worked in any combo of 2 in slots 2 and 4 only. As soon as you try to add RAM to slots 1 and 3, the iMac wouldn't boot. We tried every stick and slot position. Then we tried one single stick in each slot. The iMac would boot when the RAM was in either slots 1,2, or 4, but would not boot with RAM in slot 3.

A call to Apple was painless, and they quickly set me up with an appt at Simply Mac.The Apple tech was actually very favorable towards OWC and said they have great RAM. I dropped off the iMac AND the RAM, and Simply Mac techs found the same thing. They ended up having to replace the entire board, which has the SSD welded to it along with the RAM slots. After 7 days, it was repaired and all 128GB are recognized and operating as expected.

Hopefully this helps someone who is pulling out their hair.

Cory Cooper

May 19, 2004
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Strange, as I have used a lot of OWC RAM in my Macs as well.

Thanks for the post, as it definitely may help someone in the future with all Mac models...great troubleshooting steps there to try different combinations and slots.

Glad you're up and running, and enjoy that HUGE amount of RAM!


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