Graphical glitches on iMac Pro

Question

Level 1

4 points

Graphical glitches on iMac Pro

Hi, recently I’ve updated my iMac Pro with Vega 56 to Sequoia right from Monterey and after several days I started to notice some weird graphical glitches:

1) Apple tv app may cause screen flickering while swapping homescreen banners quickly with Magic trackpad.

2) After waking Mac from sleep the whole menubar may have a red background and reverts to normal by its own after 1-2 seconds. It becomes normal if I quickly point mouse on it either.

3) After some period of idle randomly opened Safari pages may flash red for a second on random items like side menus or even on a browser scrollbar area. It’s not stripes or noise, the whole items are covered red exactly to their exact size, even scrollbar area. And it’s always solid red color.

4) When zooming multilayered files in Photoshop 2025 their borders may have color fuzz. It’s not present if I disable GPU composition in PS perfomance settings.

I’ve reinstalled Sequoia 15.2 and all apps, tried to make a clean install of latest Sonoma and test it without any third party software - everything is same. There’s also no glitches in Safe mode. Apple diagnostics passes without errors, Memtest86 shows RAM is OK after 10 cycles of testing overnight. Temps are ok also. Continious benchmarks results of GPU test ling in Cinebench 24 shows scores about 2700 without any glitches in process. Etrecheck says overall perfomance is excellent.

Is it GPU hardware issue? What else can I do or check?

Posted on Dec 16, 2024 6:25 PM

Reply

Answer 1

Allan Jones

Level 9

72,674 points

Dec 18, 2024 9:03 AM in response to The ILM

Welcome!

—Is it GPU hardware issue? What else can I do or check?

Not much. One old test is to attach an external monitor for testing.

If the video defects repeat on the external, that is a good indicator the fault is in the GPU or otherwise on the logic board.
If the external show a clean image, the issue is in the display assembly.

—Temps are ok also.

Was that determined with temp-reporting software, from fan noise changes, or by feel?

I ask about fan noise because on my non-Pro 2017 iMac 5K, and using temp monitoring software, my CPU temps can get to nearly 60°C before the SMC ramps up the fan from its idle speed of ~1200rpm. Its normal temps while doing the basic tasks like email and word processing are 38-43°C in a room that is about 22-24C year-round.

Reply

Answer 2

The ILM Author

Level 1

4 points

Dec 18, 2024 11:14 AM in response to Allan Jones

Thanks for your reply. I’ve used macs fan control with default auto mode to check temps, idle cpu is about 40 °C, 45 and up to 65 under heavy load (Cinebench 24 continious test). GPU is up to 80°C, 35 idle. I doubt my problem is related to display panel since artifacts are presented on a quicktime screen record.

P.S. PRAM/NVRAM reset and SMC reset were done several times before every new OS installation.

Reply