Cannot upgrade RAM in late-15 27" iMac Retina

So did you ever get your ram worked out? I just installed 32GB on late 2015 iMac rretina 5k 17,1 and it accepted it but for some reason didn't allow ECC but I went with Crucial 8G sticks for Mac and besides ECC it works for now...I did notice when pulling out the samsung ram it was slower than crucial at PC3-12800S I think. Go ddr3 1866MT/s SO-DIMM and it should be good.

I also have an imac late 2015, core i7, originally with 8gb. I've recently bought 32gb from OWC and tried to upgrade. I tested all modules individually in each slot 6 times each ( memtest 2.23). All individual tests passed. Then when I put all together and test , it often fails in many ( random) tests. I simply don't know why..I'm getting crazy

You are not crazy. Same problem here.

OWC sent me new RAM thought it would work at first but then....the crash and the crash again.

Works fine with the RAM that came with my late 2015 iMac but the OWC just keeps crashing.😢

They had to replace me three times the chips I bought december 2016. This time all the chips passed the 10 loops tests. When adding 3 chips and test again they pass all tests. But when put together the four chips, they fail almost all tests...

I have the same iMac model and have had issues with updating my RAM. Bought 4 8GB sticks from OWC and had kernel panics. Tested them on Rember and discovered 1 of the sticks was "faulty." Got it replaced and everything worked fine for a few months until recently. Kernel panics started again. Did a Rember test and sure enough, it failed.

MillMusic wrote:

So did you ever get your ram worked out? I just installed 32GB on late 2015 iMac rretina 5k 17,1 and it accepted it but for some reason didn't allow ECC

That will be because iMacs do not support ECC RAM.

So I am Millmusic just replying from a different account. I apologize for the typo before. So let me repost as well. I replaced the SK Hynix PC3-14900S 2X4 stocks with the correct ram from crucial in a simple 8GX4 configuration. The machine said everything was ok but shortly after I had some major issues. Sleep/Wake problems, machine asking for first aid, IM controller warnings, and for some odd reason in the system info section the text showing my systems information and firmware was written in jumbled text that almost looked like symbols used in programming languages. I'm really curious as to any information here if possible. I did seat the ram correctly, double checked, and triple checked...keeping an eye on the machine it also started to seem to think it needed to download drivers for parts not on my specific machine. Video drivers in specific. At one point there was also a clunking sound (very faint) in the machine and it had soon after developed more serious issues like warnings about the video card, also appeared to want to slow the CPU. Fan was not audible, and the screen would light up in very bright RGB colors when shutting down. Start up was fast enough though. It was a complete mess and I currently have the new iMac in the box still to this point. I am a music producer that uses many different programs and gear if that helps.

Machine is iMac 17,1 EMC 2834

iMac 27" retina 5k

2TB fusion drive

AMD Radeon M395

Standard ram config at 4GX2

MK482LL/A

Also from reading all these posts I do understand ram can be odd in these machines so does anyone know anything about the vendor RamJet?

I'd like to replace the two 4G sticks for 8X4

Thanks

I can't comment on that vendor as I've never dealt with them; however, the two most recommended RAM vendors here are Crucial and OWC (macsales.com). Macs are extremely finicky about their RAM and it appears to work best with those two.

Thanks for replying. I had actually did the replacement through crucial 1866MT/s non parity low voltage sodimm meeting all criteria posted on Apple website. I've really been digging into a lot of info in the last month and I am clueless. OWC has had some issues as well reading other posts. I even had sought out some simple help from an apple sales rep which claimed you could configure to 64Gb on this machine but I was just trying to be safe. As far as this goes it seems to me at least, the serial presence detection might have some issues, although this is a VERY OLD topic in computing it's still much alive today. RamJet seems to be the one manufacturer to post info on this and also seem to be a bit more informative as to what is going on for some users. If anyone here has had a positive experience lasting could you please post what you are using?

Thanks.

I too have had issues with OWC RAM on the same Late 2015 iMac MAXED out 4GHz i7

Stock RAM was 16GB, bought OWC 32GB and installed them. It wouldn't boot, even with just the stock RAM. Brought it to the Genius Bar and they were able to do diagnostics and test my OWC RAM was OK and somehow got it to boot. Brought it back home but after trying out to bounce a music project, it would cause kernel panics. I even tried running Rember to test the RAM, but that would also cause panics. I was able to get OWC to send me a replacement. And for the time being it seemed fine, until I got hit with another kernel panic. However this time, it's sporadical and panics now and then, so I guess I can live with it for now...

Could you explain the nature of why not to use 16gb chips or why to keep Apple ram in configuration. From talking to multiple vendors who've tested this they are saying that the r9m395 doesn't play well with the larger capacity sticks. I can accept that. But if Apple is correct in literature real eased then doing 8gb X 4 sticks of 3rd party should be no problem. Further reading on skylake it accepts ddr3l or ddr4. Ok. But my real inquiry would be whether anything on the logic board would prevent a working combo because the 17,1 V's the 15,2 or whatever would be broadwell and skylake both having the same or near the same nm manufacturing process, hence it would seem that these machines could have some flaws. SK Hynix pc3-14900s would be in the new iMacs and those are registered dimms that Apple advises against. Guess I'm not seeing their logic.

No, I cannot - I merely pointed to some discussions from a few years ago when there were problems with a maximum of third party RAM, but not with OEM RAM. At that time - as far as I know - no one here got any definitive answers from either the third party RAM vendors or Apple except that it was clear that it did not work. And, as I said, I do not have a 2015 iMac, so I am not familiar with any of its hardware.

Wanted to chime in again and say, I hit up OWC again to warranty replace my RAM and I'm pleased to say it's working fine with no hiccups!

I read somewhere on their youtube video that they responded to a customer saying they found the fault of why their RAM kept causing kernel panics and have remedied the problem.

I also have a late 2015 5k iMac. I also put two 16gb OWC sticks into 2/4 of my slots (remaining 2 slots had the 8gb pre-seated) as soon as it arrived new in Jan. 2016 (total RAM 40gb). In Apr 2017 I started experiencing rebooting issues whereby it would not start fully, only getting to the apple icon and then restarting repeatedly. Since I live far away from an Apple Store didn't get around to bringing it in til last week. Techs removed OWC RAM and informed me that all RAM needs to be same size, so now I've got a maxed out $4000k+ computer running on only 16gb and they also told me that it can't run more than 32gb total ..the harddrive was also fried so that was replaced. I doubt that they tried reinstalling one or both of the OWC RAM to see if that still posed problems, as they indicated previously that one of the error messages disappeared once the 3rd party RAM was removed. I would be interested to hear if your 40gb RAM/mixed sizes/ OWC RAM + Apple RAM eventually ended up causing issues for you....

That ***** to hear that your HDD got fried. I have the same setup with stock 8 GB of Apple RAM paired with OWC 32 GB RAM running a total of 48 GB RAM. I kept having intermittent reboots, but stuck with it until I read they made new batches that resolved this issue. I asked for another warranty replacement (3rd time) some weeks ago and the RAM now works flawlessly! I do have to note, my RAM configuration was different as I had the OWC RAM on the top (i'm thinking that's slot 3 + 4). Now my current working RAM is configured on slots 2 + 4.