iMac 17.1 freezing - hw problem?

[urinator]

Hello,

I purchased iMac 17.1 in maximum possible configuration (32gb ram, R9 M395X, etc.) when it came out in late 2015. It has never been moved from the table and I have had no problems until recently. It is still under AppleCare which is to expire in early November.

Approximately two months ago, my iMac started freezing in a specific pattern. It would be frozen for a few seconds, then normal for a few, and then frozen again - repeating until restarted. I play a few games on it (most Blizzard games, Portal) and this issue was occurring exclusively while playing Hearthstone. Since it is just a card game, I thought it was not overloading the iMac much and assumed it was a problem with the game itself. This led me to make this comment explaining the issue further on its forums a bit over a month ago: https://us.battle.net/forums/en/hearthstone/topic/20767567812

However, since then the same issue began occurring outside of Hearthstone, mostly when playing other games, but sometimes even just watching a video. As time passes, this freezing occurs more frequently and with a worse frozen-unfrozen ratio (about 10 seconds frozen and 2 unfrozen, which makes it almost impossible to navigate to normal shut down, so I usually shut down the iMac manually.)

Of course, I did PRAM/SMC resets, reinstalled macOS, etc. I waited for Mojave whether it could fix it by any chance, but the same thing happened just a few hours after.

It feels like a hardware problem; especially as it occurs during a heavier workload, as it is getting worse and more frequent over time, however, the key issue -- which prompted me to make this thread -- is that the hardware diagnostic tool (when pressing D on boot) finds no hardware problem.

I went to the Apple Store twice to consult this in person, and they said that I just should to reinstall the macOS (which I did obviously.) Now, I asked the Apple Support about it over chat, and they were also adamant that if the diagnostic tool does not find a problem, it is not a hardware issue.

It would be quite inconvenient for me to travel with the iMac to the Store and to be without it for a few days, since I work on it from home. Since the problem is real and I can't find any solution myself, bringing it to the store seems like a clear thing to do. However, I am very afraid that based on the mentioned two visits to ask about it, and based on the chat with Apple Support in online, it is my understanding that if I bring it, they will run the same diagnostic, which will come out clean, and they will give it to me back. I was told on the chat that they do have advanced diagnostic tools, but if the one I did does not detect a problem, it is not a hw issue.

Can anyone please give me any advice? Based on my description, does it seem feasible that it is a software issue? If so, any proposed solution? Is the hw diagnostic tool reliable enough to rule out a hw issue?

Thank you very much for your time,
Simon

 

[hobowankenobi]

The first thing I would suggest would be to boot to a different drive. Any external drive should do.

You can even try network Recovery mode.

Booting to a different drive lets you take 2 variables out of the loop: The internal drive, and the OS.

If you see the same problem while booted to another drive...then the OS and the internal drive are NOT the problem. That means hardware, and something beyond the internal drive.

If you don't get the same lag while booted to an different drive, then the drive and/or OS IS the culprit.

Does it have a spinning hard drive, or SSD?

 

[urinator]

Thank you for the reply. As mentioned, the configuration was maxed out, so it has an SSD.

 

[chscag]

I would try what @hobowankenobi suggested first. You need to eliminate whether it's some software or hardware that's causing the freezing. I can tell you from my personal experience with that kind of problem, that it may be the SSD that's acting up. Disk Utility is ineffective when checking a SSD. You might want to download and try DriveDX to check your SSD. After doing all that and since you're still covered by Apple Care, it might be a good idea before your Apple Care runs out that you make a genius bar appointment and let Apple run their advanced diagnostics on your iMac.

 

[urinator]

I just bought an external hdd today and will do it soon.

The quick free diagnosis by DriveDX shows no issue. Haven't tried the paid one (yet?).

Here are screenshots of iStat menus during the freeze, but I don't see anything suspicious myself. This last freeze was just while watching a video, so the computer was not under a heavy workload.

https://imgur.com/a/C6W9UM0

 

[chscag]

Everything looks normal from iStat Menus and if DriveDX shows no problems with the SSD, it will be interesting to see what the results are when you boot from the external hard drive. Might be a good idea to check the memory modules also. Although, bad memory or intermittent memory usually will cause the machine to reboot rather than freeze. There's also the GPU which could be acting up causing the freezes but that's something that Apple's advanced diagnostics would be able to detect.

 

[Silvrbill]

I'd be suspicious of any recent apps or software you've installed.
A corrupted or unsupported file in an app or software can reek havoc with the rest of the machine.

 

[hobowankenobi]

I'd be suspicious of any recent apps or software you've installed.
A corrupted or unsupported file in an app or software can reek havoc with the rest of the machine.

Booting to Safe mode should eliminate any chance of any third party kext issues.