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iMac kept crashing - mixed ram

N

Negua

macrumors newbie
Original poster
Jan 5, 2018
8
0
In summer 2016 I bought 2x16GB from OWC and installed them in my iMac 27" which already had 4x2GB. I was in for 40GB. Unfortunately, I got kernel panics every time the computer was working a bit hard. The iMac shut down even with only OWC installed. No trouble with the original installed. OWC replaced the 2x16GB and after reinstalling I didn't have any trouble.

But a few days ago I bought X-Plane 11, and after some playing the iMac shuts down. Kernel Panic. But it seems like it's only when playing the game. So now I wonder if the mixed RAM causes the trouble? I haven't tested with only OWC installed. Should I buy another 2x16GB from OWC leaving me with 64 GB? I do a lot of editing, big files, Photoshop, Lightroom, LRT, After Affects. And I often use them all together. So it might not be a waste getting 64GB. But anyhow, will my iMac be more stable with only OWC installed?
 
These OWC 16GB sticks are totally unreliable. I had 4 of them installed in a 2015 retina iMac for a total of 64GB ram. This configuration is officially unsupported by Apple, but OWC claims it works. In practice however the iMac was freezing all the time. Many people have bad experience with these particular OWC ram sticks:
https://www.bhphotovideo.com/c/prod..._computing_owc1867ddr3s64s_64gb_4_x_16gb.html

I recommend to get rid of them and install 32GB from crucial (4*8). I just got an iMac Pro with 128GB Apple ram because I need it for the work I do.
 
Ah, you don't say. I heard nothing but good things about OWC, but since it crashed the first time, I was really skeptical, but it has worked just fine after OWC replaced them. Well, at least until now when it crashed after playing X-Plane.

Any place you recommend getting the crucial Ram?

Oh, 128GB... what are you working with?
 
I worked on a 20GB, but it took a while with my setup. Fortunately not my main projects.

Do you recommend 8*4 instead of 16*4GB?
 
Negua said:
I worked on a 20GB, but it took a while with my setup. Fortunately not my main projects.

Do you recommend 8*4 instead of 16*4GB?
Click to expand...

Yes, at least on the 2015 models. Might be different for the 2017 models where 64GB is supported by Apple.
 
Hmm, Apple says that I can have up to 64GB on the late 2015 iMac 5K retina. Or did I misunderstand? Should I remove the 2*4 from Apple and stick to the 2*16 from OWC, leaving two open slots? Or is it better to keep all slots occupied?
 
Negua said:
In summer 2016 I bought 2x16GB from OWC and installed them in my iMac 27" which already had 4x2GB. I was in for 40GB. Unfortunately, I got kernel panics every time the computer was working a bit hard. The iMac shut down even with only OWC installed. No trouble with the original installed. OWC replaced the 2x16GB and after reinstalling I didn't have any trouble.

But a few days ago I bought X-Plane 11, and after some playing the iMac shuts down. Kernel Panic. But it seems like it's only when playing the game. So now I wonder if the mixed RAM causes the trouble? I haven't tested with only OWC installed. Should I buy another 2x16GB from OWC leaving me with 64 GB? I do a lot of editing, big files, Photoshop, Lightroom, LRT, After Affects. And I often use them all together. So it might not be a waste getting 64GB. But anyhow, will my iMac be more stable with only OWC installed?
Click to expand...
i'm not sure about mac.. mix ram bus do have incompatible issue.. i'm not sure the old version is ECC RAM and normal RAM.. Those both unmatchable.. DDR3 RAM not equal with DDR3L RAM.
 
With four slots you cannot have the combination 2 x 16GB and 4 x 2GB. Each and every 27" iMac has four and four only memory slots. OWC memory is first class abd comes with a lifetime warranty. Go to their web site and use live chat.

I would remove the how many 2GB you actually have installed and just use the 2 x 16GB. And there are dozens of various 27" iMacs from 2009 so was it the correct memory as they use various types and speed modules
 
Only the 2017 iMacs support 64GB according to Apple. Previous models (2014 and late 2015) only support up to 32GB and are limited to 8GB sticks (again, according to Apple). In practice however, the 2015 models do work with 16GB sticks and up to 64GB in total, although the experience for me and many others is that this works very unstable (at least with the OWC ram). These crashes occur whenever this OWC ram is used with any configuration (2x16, 4x16, 2x16+2*8, ...).
On the other hand, I have also used other asymmetric configurations for years without any issue (2*4GB from Apple + 2*8GB Crucial).
So in conclusion, you can use whatever configuration you want, but to be save better not use 16GB sticks. I plan to request OWC to exchange my 4*16 for 8*8.
 
nambuccaheadsau said:
With four slots you cannot have the combination 2 x 16GB and 4 x 2GB.
Click to expand...

I have 2*16GB (OWC) and 2*4GB (Apple) installed.
[doublepost=1515233482][/doublepost]
Paint.It.Black said:
Only the 2017 iMacs support 64GB according to Apple. Previous models (2014 and late 2015) only support up to 32GB and are limited to 8GB sticks (again, according to Apple). In practice however, the 2015 models do work with 16GB sticks and up to 64GB in total, although the experience for me and many others is that this works very unstable (at least with the OWC ram). These crashes occur whenever this OWC ram is used with any configuration (2x16, 4x16, 2x16+2*8, ...).
On the other hand, I have also used other asymmetric configurations for years without any issue (2*4GB from Apple + 2*8GB Crucial).
So in conclusion, you can use whatever configuration you want, but to be save better not use 16GB sticks. I plan to request OWC to exchange my 4*16 for 8*8.
Click to expand...

I chatted with OWC, and they told me that they were sure they had fixed the problem (so they clearly recognize it), so their 2018 RAM wouldn't cause this problem. So they are replacing my the faulty RAM. I will ask them if they can do a 8*4GB instead. If not, I need to try Crucial.
 
I have 2*8GB (OWC) and 2*4GB (Apple) installed in my late 2015 iMac 27" 5K. Never had any problems.
 
Then this trouble might have something to do with the 16GB sticks as Paint.It.Black is saying.
 
Easy thing to try:
Take the OWC RAM -out of- the iMac, and try again.
Run 2-3 days with your factory RAM.
Does anything change?
 
Fishrrman said:
Easy thing to try:
Take the OWC RAM -out of- the iMac, and try again.
Run 2-3 days with your factory RAM.
Does anything change?
Click to expand...

It's working with the factory RAM. I now regret not upgrading when I bought it, but there should be RAM out there to support iMac. Hopefully Crucial (or the replacement RAM is working).
 
Negua said:
Any place you recommend getting the crucial Ram?
Click to expand...

Depends what country you live in, but in the UK I order it direct from the Crucial website, which lets you specify the make and model of your computer and recommends the appropriate RAM (so, under UK consumer law, they're totally on the hook if it doesn't work).

AFAIK Crucial are the retail arm of Micron - same manufacturer as the factory-supplied RAM in my iMac (and, I suspect, would turn out to be exactly the same part if you ordered the same size)
 
OWC refuses to give me 8*4 instead of 16*2 since I originally bought 16*2. So if the replacement 16*2 doesn't work, I need to sell them and buy Crucial. I live in Norway, so I need to pay around $150 in taxes. It sucks. The Crucial sticks I find here in Norway are not the same as on crucial.com.
 
You stiull did not tell us what precise model this 27" iMac was. Maybe it is too early a model to run the 16GB modules. For instance right up to the late 2014 model, the 27" iMacs can only handle up to 32GB max, and that may have had to be 4x8GB, not 2 x 16GB.
 
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