2020 iMac Screen Glitch on Shutdown

Greetings, just got a new 2020 iMac, 10-core i9, 5700XT 16 GB. It's running BigSur 11.1. I experience a weird screen issue when shutting down. The screen splits in half with the left side having a different hue. Tried it with a solid desktop color (instead of photo) and same issue. When I connected second monitor (TB Display) and shut down, the screen glitch was visible on the iMac only, not TB. Interestingly, when I turn the machine on and shut it down within say 5-10 mins NO split screen/hue glitch. But as soon as the Mac is working over say 15 mins, the glitch is evident on each subsequent shut down. I haven't observed any other issues, but to be honest I haven't ben using it much yet. Of course, I tried PRAM/VRAM, SMC resets, as well as OS reinstall, and no issues. Nothing came up on D scan. Is this a software or hardware issue? I can still return the Mac, but it would be a pain. See photo attached and thanks for any helpful suggestions, best, P.

iMac 27″, macOS 10.14

Posted on Dec 30, 2020 5:02 PM

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P3-Mac Author

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21 points

Posted on Jan 7, 2021 7:54 PM

Hello, PRAM/SMC and system reinstalls did not solve the issue. I ended up sending it back for replacement. Apple tech said that's that's likely the graphics card. Hope this helps, P.

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Feb 12, 2021 7:16 PM in response to Studioviv

Studioviv,

Thanks for posting in this thread. You gave an excellent description of the issue we're having, and I was happy to see that your problem seems to be solved.

Unfortunately, the 11.2.1 update did not solve this issue for me. I can still reproduce the issue just like the original poster (P3-Mac) indicated in the very first post of this thread, "...when I turn the machine on and shut it down within say 5-10 mins NO split screen/hue glitch. But as soon as the Mac is working over say 15 mins, the glitch is evident on each subsequent shut down."

Are you sure that this issue is completely resolved for you? If you use your iMac for 20-30 minutes or longer without allowing it to sleep, does the issue reappear upon shutdown?

I'm hopeful that this is solved for you, but disappointed that the update wasn't of any help for me...

Mike

May 28, 2021 1:10 AM in response to joohyung49

That's a good question. I think its related to the videocard types (the AMD Radeon Pro 5500 and 5700 XT i believe) and possibly there are people who are not worried at all and think it's all fine.

But it's a good question which i was also wondering about.

So the question would be. Is the issue happening on all the machines with these cards and BigSur... or on some of them?

If last, then you would think it's hardware related, and maybe also related to iOS but still also hardware...

And then Apple should explain exactly what's happening instead of keeping us in the dark about this. Sure, they are not anxcious to replace a couple of thousand videocards... but still... it's eerie quit about this issue.

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2020 iMac Screen Glitch on Shutdown