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2012 iMac - Sporadic Kernel Panics

U

uptownnyc

macrumors 6502a
Original poster
Mar 28, 2011
766
1,094
I'm trying to diagnose sporadic kernel panics with my Late 2012 iMac with Fusion drive. This typically happens when the machine has been left running for awhile. I return to find it has shut itself down. Upon rebooting, I'm shown the following screen.

http://imgur.com/7HQLzBQ

Not exactly sure where to start, or how to diagnose this problem.
 
It is a 27" and I've been running with replacement RAM since the original purchase in 2012 without incident until recently. I'll see if I can find the factory RAM. Is there anything in the screenshot which indicates that may be the cause, or you're basing that suspicion on something else?
 
Not sure whether I found the original ram or not (Found 8GB of Corsair cmso8gx3m2a1333c9) which works fine. I've been running since Saturday without a kernel panic, so fingers crossed that this solves the problem.

A few other questions. I ran the boot-up hardware test and the RAM came back OK with no errors detected. I had four 8GB sticks for a total of 32GB of Crucial RAM in the iMac when I was having the problems. Can I run with three of those sticks if I'm able to identify the one with the problem?

Crucial advertises a lifetime warranty on their RAM, so presumably if my iMac remains stable, I can RMA it back to them for modules which don't exhibit this problem.
 
Seemed to experience the same problem with entirely different RAM.
 
Would upgrading to High Sierra potentially resolve this? Obviously not if the problem is hardware, but just wondering if maybe a software issue could be the cause. Not sure how to interpret the info shown in the screen-shot, and my only option is to take the iMac into the Genius bar for help.

The other thing I don't understand is when I look in the folder where the Kernel Panic logs are supposed to reside, I don't see the expected log files there.
 
Recurrent kernel panics can be difficult to diagnose but hardware is a more likely cause.

I suppose you could create a brand new user account and boot into that for a while to try to rule out software.

Kernel panic logs are stored in Macintosh HD/Library/Logs/DiagnosticReports
 
Run MemTest.

And also try running the Mac with the original RAM. Third party RAM does go bad occasionally over time (due to heat), particularly if you buy second tier brands like Corsair, Mushkin, or G.Skill.
 
Tried with two different sets of RAM (can't find the original) and am still experiencing the problem, so unless both batches of RAM are bad (seems unlikely), I think it may be something else.
 
Well, I brought it to the Genius Bar, and they tested it for 48 hours with no incidents and returned it to me. I'd created a second user account and had them use this one -- so perhaps it was some issue isolated to my profile.

Upon return it continued to crash.

So I went ahead with the High Sierra upgrade, and it's been rock-solid for about a week. Not sure where the problem was but apparently it was software that was resolved by the OS update.
 
Guess I spoke too soon. Patched the latest High Sierra and crashed multiple times last night. Only thing I can think of now is to retire the main account I use on that machine, and move my data over to a new account. Any easy way to do that, or is it all manual? I'd already restored from a Time Machine backup after getting the machine back from Apple, so I'm assuming it's going to be a manual task.

Frustrated.
 
In spite of the Genius Bar saying the machine has no hardware issues and getting through 48 hours with it with no crashes, I still say that hardware is the most likely cause of your problems based on the nature of the kernel panic. It could be an overheating CPU (cooling problems), a failing power supply or a failing logic board.

You can go to the trouble of migrating your data to a new account but I am dubious that would end up curing it. It could be that the CPU load of the apps running in your default account bring on the panics more frequently than the clean, new user account you created for Apple.

I'd return it to Apple with your own account to test and/or just tell them to run it extra hard for a week. I'd also check the logs for any kernel panics that may have occurred while they had possession of the machine, just in case.
 
It's possible it's overheating. Yesterday was absurdly hot and very humid compared to the past week. With that said, my machine is very clean, and I doubt there's substantial build-up on the internal fans. I'll see whether the problem persists when it cools down. Maybe that'll give me some hints as to what's causing this, and I'll bring it back to Apple again if I can't resolve it. Thanks for the suggestions.
 
The software RAM test proves nothing. The Apple Genius saying they can't find hardware issues proves nothing–if the hardware problem is at all complicated the genius bar will never figure it out.

You have a 2012 iMac which is notorious for having hardware problems. Bad logic boards, bad bluetooth cards, and bad PSUs those parts cause no end of issues on those computers. I can't tell you how many hours I have wasted diagnosing hardware problems on hundreds of those machines.

Your particular kernel panic is very interesting. The backtrace specifically:
It actually points to tsc_init as the issue. This is odd because this is an early bootstrap failure. I can't say I have ever seen a computer have a tsc_init failure. It is related to determining how much time passes which is important for a "tickless kernel". Basically the OS has to understand how many ticks of the processor happen per second so everything can sync up.

The real question is why would you have a tsc_init failure at boot? Given everything I would recommend taking this to a professional who actually understands low level kernel stuff like tsc works, and can do proper hardware and software debugging. It is possible this is a software issue, or a possible hardware issue, and will require more involved diagnosis then Apple stores can provide.

Cheers
 
Thank you for your reply. I'm not even sure it's a kernel panic. I've tried a few more things:

1. Created an entirely new login on the Mac. Still shuts down.
2. Plugged it into the wall at a separate socket (it'd been plugged into an APC UPS). Still shuts down.
3. Disabled all power management. Still shuts down.

Sometimes it stays up for hours and hours then dies. Other times it dies mid-way through logging in.

I tried checking the power down cause and this is what I see:

2017-10-29 12:07:58 Previous shutdown cause: 0
2017-10-30 22:09:04 Previous shutdown cause: 0
2017-10-30 23:00:58 Previous shutdown cause: 0
2017-10-30 23:08:21 Previous shutdown cause: 0
2017-10-30 23:32:00 Previous shutdown cause: 0
2017-10-31 08:58:19 Previous shutdown cause: 0
2017-10-31 09:13:06 Previous shutdown cause: 0
2017-10-31 09:20:37 Previous shutdown cause: 0
2017-10-31 09:30:30 Previous shutdown cause: 0
2017-10-31 09:42:51 Previous shutdown cause: 0

From what I've seen this indicates a hard shutdown and the suggested course of action is to check the power button, but I'm assuming that may not be the actual problem.

I've tried looking into some of the other logs, but I'm at a loss with the details in those. Would a clean wipe and re-install of MacOS help, or is this likely just futile until the cause is diagnosed to not be hardware?

It's a 2012 machine, so I'm just tempted to wipe it and get rid of it, but if the problem is software, the last thing I want is to migrate my issue to a new Mac when I do my restore from Time Machine.
 
Last edited:
I had something like this issue with my
Apple iMac "Core i5" 2.5 21.5-Inch (Mid-2011) aka 12,1

It would freeze and then kernel panic.

I tracked it down to bad RAM that I'd upgraded myself just after purchase. Crucial replaced the RAM in 2015 under their lifetime guarantee/warranty. It's been fine for the last 2 years.
 
msephton said:
I had something like this issue with my
Apple iMac "Core i5" 2.5 21.5-Inch (Mid-2011) aka 12,1

It would freeze and then kernel panic.

I tracked it down to bad RAM that I'd upgraded myself just after purchase. Crucial replaced the RAM in 2015 under their lifetime guarantee/warranty. It's been fine for the last 2 years.
Click to expand...


Did you test your RAM yourself and determine it was faulty? My tests haven't found that to be the case, and Apple's tests didn't find that either. My RAM is from Crucial, but I'm reluctant to send it back to them if it's not known to be the cause.
 
uptownnyc said:
Did you test your RAM yourself and determine it was faulty? My tests haven't found that to be the case, and Apple's tests didn't find that either. My RAM is from Crucial, but I'm reluctant to send it back to them if it's not known to be the cause.
Click to expand...
RAM tested fine.

I knew the RAM was the issue aI my iMac only panicked when the Crucial RAM was inserted.

Happy to provide email history if it is useful.
 
Unfortunately, this problem persists, rendering my iMac unusable.

Things I've tried:

  • Brought my iMac to the Genius Bar and they ran it for 2 days without incident.
  • Ran the basic hardware diagnostic tests and encountered no issues.
  • Ran the extended hardware diagnostic tests and encountered no issues.
  • Ran a multi-pass RAM test with no problems detected.
  • Ran it with some alternate RAM and it crashed.
  • It's now cooler in my house, so heat shouldn't be a factor.
  • Tested the drive with FirstAid without an issue.
  • Re-installed MacOS and upgraded to High Sierra -- still crashes after the upgrade.
  • Restored from a TimeMahine backup.

For awhile my system ran for about a week, then finally crashed. The other day, after performing an extended diagnostic test and rebooting, it crashed again on boot-up after entering my password.

When I search the logs in Console.app, I don't see any matches related to "kernel panic" so I'm inclined to believe that perhaps this isn't the cause, but the logs in the Console.app are so extensive that I'm not sure what else I should be looking at.

So I'm kinda at a loss. I'm starting to wonder if maybe it's a software issue. I suppose I could backup everything, wipe the machine, and re-install High Sierra, then incrementally re-install the stuff that I need. My concern there is the potential loss of things like my Photos library, but I suppose I'd always have the TimeMachine backups. Woudl I be able to selectively restore individual things like that rather than performing a full restore?

I've got another Genius Bar appointment scheduled, but I'm not sure that they're likely to uncover anything new.
 
I'm sure I'll jynx myself by posting this, but this problem has just disappeared. I've run for well over a month without any reoccurrence, but also no explanation as to why it's now working.

I never did follow through with the final Genius Bar appointment, because it was stable.

I'm stumped.
 
Well the problem returned. Sometimes the machine would last an hour before crashing. Other times it'd last a week.

I'm currently in the middle of the RMA process with Crucial so we'll see what happens when I get a fresh batch of RAM.
 
Fresh RAM and same problem. Had Apple swap out the internal power supply for ~$150. We'll see if that helps.
 
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