Chosen Solution
[Edit: the system runs fine after having replaced the built-in SO-DIMMs with the ones from OWC - i.e., 2x16 GB, but I’d still like to know if they should be compatible to install both together]
I bought an iMac with 8 GB of memory, and separately 32 GB from OWC. I tried to install the two 16 GB sticks into the empty slots, and even though the computer booted fine, it went into a restart/crash loop after running for about 60 seconds. Before it crashed the first time, I saw the memory tab in “About mac” and it showed all 4 modules as correctly installed. I’ve since removed the sticks and I’m currently only using the two built in 4 GB sticks in their original slots (never removed them) and the iMac boots and runs smoothly, but I’d preferably like to install the other two sticks too. What’s the best way to debug the issue? Should I try removing the original RAM and inserting the OWC RAM sticks into the same slots? Thanks!
Since you got these RAM modules from OWC, I would suggest that you contact them directly and have them assist you with this. I would think the first thing would be to double-check that these modules are the correct ones for your Mac. Your Mac also should have “built-in” instructions on how to properly add the additional memory and to what slots when using modules of different capacities. FWIW, I have been an OWC customer for years and have only had the best experience with their products and their support staff for things just like this.
Which slots have the 4 GB DIMM’s and which have the 8 GB DIMM’s. I’m wondering if the newer logic boards can’t handle mixed banks. Here’s a bit more Understanding What a Memory Bank is Take the time to read the follow up links as well.
