Chosen Solution
After working from home for a few months and seeing my late 2015 iMac (17,1) struggle a little bit I began looking into upgrading the memory. Apple’s website says the max capacity is 32gb, but I see ifixit, owc, and a couple other places showing that 64gb is possible as well, using 4 x PC3-14900 16 GB RAM chips. I purchased this memory here at ifixit and when I tried to upgrade to it the memory is not detected. I have tried all four sticks of memory I purchased in different combinations of slots, but the only memory that shows up when I go into About This Mac are the OEM sticks that came with the iMac. If I only have the new memory in the computer it doesn’t turn on at all. I get a single beep once every five seconds, which the apple support article says means “no ram is installed.” Is this just incompatible ram, even though it’s being sold as compatible, or might I have another issue I need to address to make the ram work?
Are you sure you have the correct model? The Mid 2015 27” iMac uses 1600 MHz PC3-12800 DDR3 and won’t work with the Late 2015 1867 MHz PC3-14900 DDR3 SO-DIMM’s. You’ll need to contact the iFixit store folks to exchange out the RAM if thats the case.
