Q: Cannot upgrade RAM in late-15 27" iMac Retina
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Jan 18, 2016 7:50 PMby babowa,I do not have a late 2015 iMac, so I do not know if the problem that were evident with 2010 iMacs could be similar; before linking of a couple of those old very long threads, the crux of the problems was: the 27" iMacs would run happily with all factory RAM, or with less than max (12 GB ) of a mix of OEM and third party RAM, but would have problems with maxed 16 GB of third party RAM. I used to have such a 2010 and stayed with a total of 12 GB of RAM (4 GB OEM and 8 GB of OWC RAM) which worked fine.
Problem with 16GB on 2010 iMac 27" i5 & i7.
New 27" 2010 iMac i7 Memory Issues
Other than the usual suspects such as faulty RAM, RAM slot, or not seated properly, if you have time, you might want to try to install less than the maximum - it's a shot in the dark, but....
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Jan 19, 2016 5:34 AMby arthurfrombeverly hills,Thanks for the reply and the links. After reading many of those old posts, it's clear there's a "Apple" RAM vs. aftermarket RAM incompatibility. Scarier still, now I'm wondering if my iMac will even run at all maxed out at 32GB (assuming I add "factory" RAM from macramdirect.com--some users apparently had issues with maxing-out older iMacs). If that's the case, I'm ready to have at it with Apple. I did not pay $$$ for a machine that won't work as advertised.
As to your suggestions ...
There is no problem with the iMac itself. All the RAM slots work fine (I've moved the factory RAM sticks around with no issues whatsoever; as soon as I add aftermarket ... kernel panics).
Obviously, I'm seating the sticks correctly. I know what I'm doing (and have zero issues when the factory sticks are used alone).
It's not faulty aftermarket RAM. I've been through three sets now and all have failed.
It's not incorrect RAM either. The last pair of modules I tried was from OWC and is the set said to be "compatible" with the 27" iMac Retina (http://eshop.macsales.com/item/Other%20World%20Computing/1867DDR3S16P/). To their credit, they are refunding my money.
It's beginning to look more and more like the only option, if I want the full 32GB Apple claims this machine can run, is to ditch the factory sticks (two 8GB modules) and install four new 8GB modules of aftermarket RAM.
Mostly, this is a joke. Can you imagine if adding, say, an external hard drive was this problematic?
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by dialabrain,Jan 19, 2016 6:17 AM
dialabrain
Jan 19, 2016 6:17 AM
in response to arthurfrombeverly hills
Level 5
(5,800 points)
Mac App Storearthurfrombeverly hills wrote:
It's beginning to look more and more like the only option, if I want the full 32GB Apple claims this machine can run, is to ditch the factory sticks (two 8GB modules) and install four new 8GB modules of aftermarket RAM.
FWIW, that's exactly what I did for my 5k late last year. I've had no memory issues and they are the same modules you purchased.
I vaguely remember years ago it was not recommended to mix different size modules not just for Macs, but PCs as well. It's been too long to remember the details. As far as mixing Apple and OWC modules, even though they spec the same there may be some subtle difference causing an issue.
I have just stuck with the same size/same manufacturer rule when it comes to memory and so far that's worked out.
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Jan 19, 2016 8:01 AMby babowa,Well, that depends on which mfr's RAM Apple is using nowadays (since Apple doesn't manufacture RAM). You'd have to look at your original RAM to see.
And, if it is an odd compatibility problem, the 2010's did not work with maxed out aftermarket RAM - to be maxed out, you had to go with OEM RAM. It's never been my experience not to be able to add the correct specs of RAM from OWC; Apple has no cautionary instructions on what RAM to add except they do need to be the exact specs and preferably from a vendor who actually tests the RAM in Macs (rather than just saying it's "Mac compatible"). You should also always install it in matching pairs (new iMacs have the RAM installed vertically and you need to match - from the top - slots 1 + 3, and slots 2 + 4; older models have two horizontal rows and you match the upper and lower horizontally). Oddly enough, Apple has not changed the graphic in About this Mac/Memory - it still shows it the way the older Macs' RAM was installed, which does not help in dispelling confusion. Macs have always been very finicky about their RAM (among other things).
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Jan 19, 2016 10:51 AMby Gingerbread,I don't know whether this is of any help to you but I recently ordered 2 x 8Gb Crucial ram for my Late 2015 27 inch iMac bringing total memory to 24gb and it runs flawlessly, even though they are not in pairs! When my iMac arrived and I opened it up to put in the memory I noticed that 4gb was in bank 0 and the other 4gb was in bank 1 so I just added the new memory in the vacant slots and it works. I did notice, however, that the modules were a little hard to push in and required gentle force. I have always used Crucial memory and never had a problem with it. Perhaps the problem is with maxing the memory out rather than the modules themselves.
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Jan 20, 2016 8:37 AMby arthurfrombeverly hills,Thank you for that interesting info. I suppose it's possible that adding just one aftermarket stick, boosting my RAM to 24GB but not the full 32GB, would work. As I think someone else mentioned, maxing out the RAM apparently requires all-identical modules.
I'm going to look into finding a source/match for my factory RAM (which I believe is Samsung).
