Pending on you and more folks doing this testing on the 27-inch variant (whose access to RAM is a lot easier than the same on the 21.5-inch variant, which is what I’m using at the moment), you might be able to help provide a clearer sense of the hardware and firmware’s limits with respect to RAM configurations. So yes, give it a whirl and let us what you learn from testing it on your 27-inch model! And from the look of it, wasn’t on here for long.ĭIY experimenting and testing is how a lot of us on Early Intel Macs (soon to be the home of Ivy Bridge/Haswell iMacs) forum and the PowerPC Macs forum keep older and vintage Macs running well above and beyond what Apple intended or even planned. gave it a go and reported it didn’t work out, but didn’t do the more rigorous tresting of reviewing kernel panic logs or other RAM testing (like memtest) to determine why it didn’t work out. The optimal way to know is to do the experimenting and testing yourself - knowing full well the risk (well, more time than risk) in doing the work to swap out the RAM may not yield hypothesized outcomes.

Hope other people keep pushing it and I may try again in the future. I got farther than I thought I would and getting the Imac to even boot with it was neat.

Maybe with 10.16 coming later this year there will be another bootrom update and maybe these High capacity chips will work in older 2013 Imacs. There may be more compatibility with the Haswell Cpu's, Don't know till we try? It would be interesting to try the same chip 16gb DDR3L 1600 chip on a 2014 or mid 2015 Imac. One thing I haven't tried is running it with Win10, and at this point I won't since I've played with this enough and these chips are going back in the mail before I brick my wife's Imac, but if somebody were to run Win10 and see if it's a MacOs limitation or Hardware compatibility that would be another clue. At 51C, but that shouldn't be effecting the system. I checked the Dimm temp's and the 16gb chips do run a bit hotter than the 8gb chips. So at some point there is a degree of the CPU recognizing the Large ram chips but it's not able read from them entirely correct. I tried running it with 10.15.4 and it's still unstable. Unfortunately today after a few hours I got Kernel panics with it in 10.14.6.

Imac 27 late 2013 memory upgrade