Late 2015 27 iMac 5k RAM spec

PhoenixFnX wrote:

Again, another mistake in the conclusion, it is the opposite :

1866MHzCL10 is 5% faster than 1600MHzCL9 and surprisingly, it it 5% more expensive 😉

R U sure this time?

Thanks for posting this question - I just got my first iMac ( 27" late 2015 model) and all the info your post received helped me choose and install this memory Crucial 16GB Kit (8GBx2) DDR3L 1866 MT/s (PC3-14900) SODIMM 204-Pin Memory For Mac - CT2K8G3S186DM (from Amazon.ca) . I have 24 GB of RAM now, and will be doing music and photo editing. Everything is working fine (past 2 weeks) and I will try to post more later, once I get more experienced at all the editing.

Please look at the CAS Latency CL as well

OWC has CAS latency CL =11 and Crucial I think has 13 .. lower Latency is better in Random-access memory (RAM)

I hope this helps !!

I'd assume that the OP has purchased RAM by now - after all, they posed the question 8 months ago and have not returned since.

raripps I have had the same problem with 64 GB of OWC memory in my late 2015 27 Imac. Were you able to get it to work?

What was the outcome with OWC and did you try an alternative brand? I installed 64GB (four sticks of 16GB) twice and experienced the crashes and logging out etc. So for the second time I'm returning the RAM and requesting a refund. I ran memory tests and they all failed.

I've never had a issue with OWC ram so this is a new one for me. The reviews I've read on forums and B&H have stated the same issues and crashes I'm experiencing.

I'm purchasing two 16GB of ram from Crucial and will update here. If that goes well I will purchase another set.

Hey Phillip - I am having the same issues as you are (and bought them through B&H although working with OWC directly to get replacements). If I use the 4x16 GB modules from OWC I get several kernel panics over the span of an hour, and the occasional WindowsServer crash forcing a re-login. If I use the memory that came with the computer or a 4x8 GB set I bought from NewEgg it works fine.

I too am getting to the point of asking for a refund. Has anyone gotten this memory to work? I ran Apple hardware diagnostics and the memory came up fine.

Has anyone tried re-installing the OS and apps from scratch to see if that works? That would be a huge pain for me, but I'd do it if it works.

Hi Philip, I'm one of the original posters and first to use the OWC 16GB ram chips. To date I have 32GBs of OWC ram and the original two 4 gig ram chips that cam with the computer from apple for a total of 40GBs. I am running Adobe Photoshop CC, Lightroom CC, Final cut pro and lots of other software with no issues to date. I have the top of the line iMac 5K when first introduced in late 2015. I'm currently running the OS Sierra with no issues.

Not sure what's going on with some of the computers but it could be a particular software that might be causing some of the issues. Try comparing software with each other to see if you can pin point which one may be the culprit, that could be the case. If I recall, there was an issue with the newer version of Microsoft office but I'm not sure. Just in case I'm still running the Microsoft Word 2011. Hope this helps.

Rick.

Hi MyronK - Yes, after two orders of 64GB I returned the RAM to OWC. I continued to get kernel panics and errors when running Apple diagnostics. When reverting back to to the original Apple memory the issues were resolved. I purchased Crucial's RAM, four sticks of 16 Gb and there no more kernel panics. When running Apple diagnostics, they came back clear.

The memory I purchased was two sets of Crucial 32GB kit (16GBx2) DDR3L-1866 SODIMM Memory for Mac : CT8017544. Hope this helps.

Thanks Phillip - I just got a third set of 4x16GB OWC RAM and it's the same story all over again. Apple Diagnostics fails, Rember fails at the beginning (can't even do 1 loop) and more kernel panics. I am going to ask for a refund and look to get the Crucial memory instead.

It's a shame because OWC seems to have a good reputation, but apparently these latest batches of memory are just bad. The rep told me that they did have some issues with some batches but the problems were taken care of. I guess not.

There was a similar problem with the 2009/2010 iMac models, discussed in these lengthy threads - basically, putting in less than the max of third party RAM worked and using max OEM RAM worked, but using the maximum of third party RAM did not. Don't know if this is a similar problem, but it sounds like it, so I am linking to the old threads:

https://discussions.apple.com/thread/2567907

https://discussions.apple.com/thread/2588800

Apple states that the iMac 27"Late 2015 model can have a maximum memory of only 32 GB (that's 4 DIMMs of 8 GB each)

Late 2015 27 iMac 5k RAM spec

Maybe the 16 GB DIMMs that OWC sells don't work properly on this system or can end up causing these memory issues everyone is talking about.

That's probably why Apple only recommends the 8 GB DIMMs.

Can this be the reason?

I cannot state with 100% certainty that this would be the case or not. The fact is that when Apple publishes their maximum supported numbers, they've tested it to that number. Third party vendors such as OWC test it with more RAM and, if there are no problems, then states that it's been tested with more. And, in 9.8 out of 10 cases it works well, just as advertised. I had 12 GB installed in my 2010 - more than the 8 GB recommended by Apple (and less than the max 16 GB) and it worked great. At the time, and after reading about all the problems, I decided to keep it below the maximum with third party RAM.

I don't believe there was ever a definitive and conclusive answer to the problem at the time (at least I have not seen one here).

And, FWIW, I still use OWC RAM - currently only in my MBP as my newer iMac came with 16 GB and so far, that has been more than enough for my needs.

And I put 20GB in my 21" iMac many years ago, still working fine.

Congratulations!!! Thank you for the feedback! I've been looking every corner of the Internet for months...what machine do you own? It was crucial sticks 16X4 or something else?