Hi friends!
I hope you’re all well in these strange times.
I’ve enjoyed a good 6 months of perfect use out of my 2019 27" iMac, only for it to start rebooting on me.
It started while doing a fair bit of video editing and the intense Zoom use we’ve all gotten used to recently, when it shut down and rebooted displaying a pre-boot error message.
It happened a few times to where I began to suspect a RAM problem. As I’d seen suggested profusely online, I bought my iMac with 8Gb of RAM which I upgraded with 2 sticks of mac-ready 16Gb from Timetec. I installed that on the day I received my mac, so it’s never caused a problem, but my immediate instinct was to blame the unholy non-Apple devices.
But a day-long memtest86 test seemed to hint at the Hynix sticks my iMac shipped with being faulty (I unfortunately couldn’t get the report as memtest froze after the end of the test).
So anyway, I’ve removed the Timetec RAM sticks and left the original ones in, and I’m using my mac to write this post before I go back to memtest with just these original sticks in and see what’s up.
In the meantime, I wanted to ask if any of you had this sort of issue (reboot without warning under all-things-considered-normal strain, crash log mentioning kernel panic but also, in the latest, cpu panic, which is new) and what you did to fix it.
Yes i have had the same thing happen to me, albeit on an older iMac. I also upgraded memory and after initially running just fine, the mac suddenly gave a big “tuuut” sound and rebooted. Removing the new memory modules permanently fixed the problem. Its a long time ago and i don’t remember which brand dimm modules i used but they must have been of inferior quality.
Hynix Is a good brand but it could be a chip on wrong on that module. In my case, the mac failed within a day so it was clear the memory was no good.
You could put it back and do your memory stress test again to prove for certain something is up with one of the modules. If there is, you will have to replace it. Normally there is no warrantee on memory modules but you may want to check your receipt.
Thanks for taking the time to reply! I’m glad my troubles seem familiar although I’m sorry you had the same problem.
I’ve tested all the modules but one and they’re all good, so far, actually. So either this last one is the faulty one or there was something else going on that was giving my errors the first time around. (Note that according to Memtest, the Hynix ones are fine, actually!)
I keep reading about clearing NVRAM too, which I haven’t done, and I remember Steven mentioning it on MPU a while back.
I’m wondering if that’s something that could create that sort of self-reboot issues…?
Anyhoo I’ll be testing that last module later today, I’ll update here accordingly. I’m hoping it’s as simple as this last stick being bad…
Thanks again!
Thank you! I did the Apple one first but for some reason felt compelled to go with another opinion. I actually went for Memtest, which you’re recommending here!
Are you sure it is the iMac and not software. The only reason I ask is that a lot of the various forums are talking about increased random reboots due to the latest software update for Catalina (10.15.4). Just a thought
That’s a very valid suggestion, thanks! Actually, I started with that because my very first reboot was with Handbrake. Handbrake (video conversion tool) has a documented tendency for that sort of crashes so I immediately assumed it was the culprit and removed it. But the crashes kept happening, usually when video was involved.
Now, I am tech savvy but not low-level, bare metal tech savvy, so I don’t know for sure that video is RAM intensive, but I would assume so, hence me looking at my RAM sticks, especially the after market ones I’ve installed. After all, this is my very first Mac, so I’m learning.
But right now, memtesting the sticks one by one is seemingly returning no error, so I’m kind of at a loss. The last one is still running so we’ll see but I will do the option/command/P/R thing next and see if the crashes happen again. I’ll double check that Handbrake is gone for good too (I must confess I’m not completely clear on how to remove mac software…you just drag it to the trashcan?? As a lifelong PC user, that sounds paradoxically counter-intuitive ).
Thanks!
short answer: yes (some apps have an uninstaller, tho)
Long answer: there are utilities that clean up some cruft left over when you drag the application to the trash. You can read something more in this topic.
Thanks for this, I’ll definitely look into cleanup solutions!
That said, all my RAM modules came out clean from Memtest…Until I put them back together.
Not sure what’s up with this but the combination of these modules makes them prone to errors…? That’s a thing?
My 2015 iMac completely died on me a month or two after the warranty had expired. I took it to someone else to take a look to see if there was a cheaper way to get it fixed. The guy couldn’t get it fixed so I took it to Apple Tech Support. They needed to change the whole logic board. Because someone else had opened my device, they would not take my old board. This means that they charged me double, that is, the “full price” instead of the “replacement price”.
They had me pay upwards of USD2000 for this replacement.
Just to say that honeymoon also ended abruptly for me.
Interesting insight, thanks! Sorry you had such a bad experience!
I don’t think I’m there yet in terms of problems, I just need to figure out whether there’s a science to how to plug RAM in the iMac, I’ve seen mentions that the order you put your modules in can have an effect. In fact, I’ve tested that myself, where my mac wouldn’t book unless I’d move my module to another slot.
As for Zoom, we’ve raised concerns to my employer, but they reassured we were using a professional setup that wasn’t subject to the same weirdness that was affecting the consumer version. I’m ethically bugged about this but it’s become such an unavoidable software in a matter of days…
An update, for those who were following this topic:
After memtest-ing all the RAM modules one by one and having no error that way, I presumed the two couples weren’t cohabiting harmoniously, so I opted to only use the two 16Gb modules I bought and forego to the 8Gb Apple shipped my iMac with. I’m thus down to 32 Gb instead of the 40Gb I could have but I haven’t had a single crash since!
Thanks for those who submitted help and suggestions here! Computers are weird, man!
(some apps have an uninstaller, tho)