Chosen Solution
It happens especially when using graphics or video programs. I tried everything. Would you please give me some advice? reset NVRAM - donereset SMC - donenew fresh installation - doneI connected the second monitor, and the flickering continues on the second screen at the same time.I used the screen recording, and everything seems fine in the record; there is no flickering in the screen record, but there was a lot of flickering in real-time. So, the recording shows nothing. I guess it is not a screen hardware problem (the second monitor has also flickering when I connected) What do you think? Is it about the GPU, graphic card, or processor?
Clearly the logic board has an issue. I would still recommend running the onboard diagnostics to see if anything pops for an error. Apples diagnostics are a bit limited, it can’t test the GPU its self so you may not get an error. There is no GPU board in your system, the discreet GPU is soldered to the logic board. But I’m not sure if the issue is the GPU chip its self or the video RAM. While not exactly your system the layout is the same iMac Intel 27" Retina 5K Display Teardown Jump down to Step 8 to see the GPU (Red) and video RAM (Yellow). If you have someone with a chip rework station they might be able to reflow the RAM chips if one has a bad solder joint. Otherwise its time for a new logic board Your logic board options: Retina 5K Logic Board, 3.4GHz i5 QC, 570 4GB, Apple P/N 661-03378Retina 5K Logic Board, 3.5GHz i5 QC, 575 4GB, Apple P/N 661-03379Retina 5K Logic Board, 3.8GHz i5 QC, 580 8GB, Apple P/N 661-03382Retina 5K Logic Board, 4.2GHz i7 QC, 575 4GB, Apple P/N 661-03383Retina 5K Logic Board, 4.2GHz i7 QC, 580 8GB, Apple P/N 661-03384
