Installed maximum 4 x 8gb memory modules into iMac 27 late 2013 i7 3.5 ghz quad. Crashing hourly reporting kernel panics. What is the fix? Less memory?
iMac, OS X Yosemite (10.10.2), 27 late 2013 3.5ghz i7 fusion quad
Exactly what make of RAM did you get and exactly what RAM specifications did you get?
Unless you got either Crucial (direct from Crucial) or OWC (www.macsales.com) then you likely got either cheap incompatible RAM or the incorrect specs or both.
It's possible that the RAM chips you've installed aren't one of the known 'good' brands. There are lots of threads on here where users have experienced exactly the problem you describe with some RAM modules. The solution is normally to drop down to less RAM or, better still, swap the modules for known good brands:
Thanks for your comments. The RAM is direct from Crucial UK and they specified it over the phone for my iMac. I get the feeling from the blogs the 27 late 2013's don't like 32GB. If this is the case is there a maximum that it will be stable with? Can I mix the original 2 x 4GB Apple modules with say 2 x Crucial 8GB modules? (20GB)? Or should I limit it to just 2 x 8GB? The Crucial memory is labelled CT8G3S 160BMCEU, 8GB DDR3L 1600 SODIMM MAC.
Yes, you can mix/match. Put back the original RAM in the slots they were in (I assume that would have been slots 1 + 3 from the top (of the way you are looking at it) and then put in the other two in slots 2 + 4. This will result in a pic graphic in your system report as having them matched horizontally which is the right thing (don't ask - Apple changed the configuration of the slots, but not the graphic of it).
There was a big problem with 2010 27" iMacs not accepting the full complement of third party RAM - as long as you had the OEM RAM and didn't go to the max total, the third party RAM was fine (while they were fine with all OEM RAM). So, maybe that is still a concern - I don't know. I'd definitely say try it with 2 of the RAM modules from Crucial. If that works, simply try to return the others as not compatible.
You may have just one bad module. See if you can install two modules at a time and test. Repeat until you determine which module or modules are causing the problem. Then talk to Crucial and have the replace the faulty modules.
marcfromlondon wrote:
... I get the feeling from the blogs the 27 late 2013's don't like 32GB. ...
This is only true if RAM is of mediocre quality or if there is in fact a bad
chip.
I had installed 32GB of PNY memory that was supposedly Mac compatible
in my 2013 27" iMac and had all manor of issues similar to what you had.
When it was running Mavericks, the issues were occasional but became
exacerbated after the Yosemite update. I replaced it with 32GB of OWC
RAM and have been running problem free ever since.
Thanks all - in particular babowa. I removed 2 x 8GB crucial modules and reinstalled the original Apple 2 x 4GB modules as you suggested - reducing memory from 32GB to 24GB. Machine is now stable. From this experience and comments from others the most likely cause is that the machine cannot run stable with a full compliment of 32GB of third party (Crucial) memory - only Apple supplied modules seem to be work. But you will have to pay twice the price.
This is only true if RAM is of mediocre quality or if there is in fact a bad chip.
That may or may not be the case with 2013's, but it certainly was an issue with 2009 - 2010's and some 2011's; here are two of the rather lengthy threads at the time:
New 27" 2010 iMac i7 Memory Issues
Installed maximum 4 x 8gb memory modules into iMac 27 late 2013 i7 3.5 ghz quad. Crashing hourly reporting kernel panics. What is the fix? Less memory?
