Graphic issues on Late 2012 iMac

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Level 1

14 points

Graphic issues on Late 2012 iMac

Dear community,

on my iMac are randomly appearing Graphic issues. Suddenly, while working, these black triangles starting flickering around screen. (like seen on these picture). Even on an external monitor.

A system restart helps for the first time. But after a few working minutes or hours, the problem occurs again.

System is running Catalina on an external SSD.

AHT fails: Cannot Load 'EFI/Drivers/TestSupport.efi

GT640M Nvidia

Is there someone out there who knows if that is a hardware error?

iMac 21.5", macOS 10.15

Posted on May 25, 2020 6:34 AM

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Answer 1

DaveL93 Author

Level 1

14 points

Jun 3, 2020 3:41 AM in response to BDAqua

Thais for you answere.

I intsalled MacsFanConrtoll and temperatures seems to be ok. Nether then less I raised the fan speed up.

CPU aorund 131F or 55°C

GPU around 121F or 50°C

Even when these problems start to occur.

But I made some more analysis.

The process windowserver needs a lot of CPU und GPU power. Up to 70% CPU and 40% GPU. And needs over 1GB of memory.

But I have connected a 4k monitor via DisplayPort.

I installed HWMonitor. HWMonitor lists 448°F on HardDrive Bay 1 . Bay 2: 264°F. These sensors won't show up in FanControll.

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Answer 2

BDAqua

Level 10

251,379 points

Jun 3, 2020 3:32 PM in response to DaveL93

448°F & 264°F ???

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Answer 3

BDAqua

Level 10

251,379 points

May 25, 2020 10:26 AM in response to DaveL93

Have you blown the dust out of the intakes lately?

What temperatures does this App report? Especially the GPU.

This App can be used to speed up the fans, all my iMacs would be dead without it.

Never ever ever drop fan speeds below the speed that the Mac itself is calling for.

MacFansControl…

https://www.crystalidea.com/macs-fan-control

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Graphic issues on Late 2012 iMac

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