iMac 27" 2017, graphical glitch on shutdown

[user1234]

Hi!

I get a graphical glitch when I shut down my iMac. It's looks different from time to time, and it reminds me of the look you get with a failed GPU. The computer works fine except for this though, even under very heavy load (video editing and exporting, graphics accelerated photo editing, X-Plane 11). This shows for a couple of seconds after shutting down the OS, just before it powers off.

If I remember correctly, this started with High Sierra. Currently on 10.13.1.
iMac specs: 27" - 2017, i7 4.2 GHz, Radeon Pro 580 8 GB

Has anyone else seen this on their iMacs? Also, my Magic Trackpad sometimes disconnects on it's own repeatedly, but that's probably unrelated.

 

[killhippie]

have you tried booting into recovery and reinstalling 10.13.1 without wiping the drive so you keep all your information? I have not seen that on my 2017 iMac same GPU and CPU with a 1TB SSD. It did occur on some 2015 iMacs though, there was a thread on it in the Apple forums. I would contact Apple tbh as it could be a failing graphics card, although they may want you to reinstall 10.13.1 from scratch to make sure. When updating to a new OS thats when these things sometimes show up if there are issues lurking in a machine. https://discussions.apple.com/thread/7685288?start=0&

 

[user1234]

I have not tried that. I was hoping to avoid that, as it would require some work to set things up properly again. I have quite a few applications that will have to be reinstalled if I reinstall the OS even without a wipe

 

[T'hain Esh Kelch]

Does look like a GPU issue to me too. I would also recommend a reinstall of the OS, and see if that helps. Could just be some kext got the hickups. If that doesn't work, definitely take it in to repair under warranty.

 

[user1234]

So here's what I'm going to do. I'm going to create a separate volume and install a fresh copy of High Sierra (thanks APFS for volume space sharing!). If that does not work then I'm going to create a partition and install Sierra on.

If that does not work I will contact Apple, but I'm pretty sure it's a software thing and I'm not keen on driving for an hour (or more for an official Apple store) to have them find nothing wrong.

I'll report back!

 

[chedder’mac]

I’ve seen that issue on a late 2015 27” maxed out system...talked to Apple about it, the recommended to reload the OS, it was Sierra at the time, and try different things such as video editing and playback programs. Well it didn’t do it again until I reloaded VLC player, then the issue came back (it was only on shutdown, never any other time) so reloaded again, left off some programs and the issue hasn’t come back.
If it does it’s off to the Apple store under Applecare+

 

[user1234]

An update:
I installed High Sierra fresh on a new APFS volume, and it did not show this glitch on shutdown. I tried several shutdowns and no glitch. Then I encrypted it with FileVault and the glitch appeared on every single shutdown. After disabling FileVault again (it's interesting that it took 30 minutes to encrypt, and 2 hours to decrypt) the glitch is still present, but now it happens almost immediately after the OS starts the shutdown process. The glitch appeared above the wallpaper, rather than on a black screen. It is confirmed to be a software issue.

I will be sending Apple some extensive feedback on this matter, and hopefully it will be fixed soon.

 

[Fishrrman]

OP wrote:
"If I remember correctly, this started with High Sierra. Currently on 10.13.1."

If you see it ONLY using 10.3.1, and NOT under any other version of the OS, it's "software", not hardware.

I'd consider it a software glitch (perhaps a re-install of the OS would get rid of it), and not worth losing much sleep over.

Perhaps with the next iteration of High Sierra, it will be gone.

 

[user1234]

OP wrote:
"If I remember correctly, this started with High Sierra. Currently on 10.13.1."

If you see it ONLY using 10.3.1, and NOT under any other version of the OS, it's "software", not hardware.

I'd consider it a software glitch (perhaps a re-install of the OS would get rid of it), and not worth losing much sleep over.

Perhaps with the next iteration of High Sierra, it will be gone.

It started happening with 10.13.0 if not sooner. In my post above you will find that I did a fresh install and the problem went away until I enabled filevault. It's definitely software at this point.

Apple have received a bug report, but unfortunately there is very little room to write, so I had to simplify it a lot. Hopefully they will contact me asking for more info if they don't already know about it.

 

[greyeyezz]

This would happen with my late 2015 27" 5K running Sierra 10.12.3. Very intermittent. Since 10.12.4 it hasn't happened again.