MacBook corrupted frame buffer

[blueskull]

Apple gurus here, have you encountered similar things in the past?
LCD shows corrupted pixels preboot, but once main OS is loaded, there's no corrupted pixels anymore.
ADP and a third party user space memtest all checked out okay.
Corrupted pixels are fixed by moving cursor near it, but if cursor moves too fast, there are new bad (white) pixels created along the path.
Preboot mode don't display on external monitor, so I can't tell whether the LCD's internal frame buffer is corrupted or the iGPU's frame buffer is corrupted.
I saw similar issues with my previous MacBook (both 2017 12 inch), but the old one has fewer corrupted pixels. Both are perfect once main OS is loaded.

And ideas?

[Berni]

That's an odd issue alright.

If it only has an integrated GPU then video memory is in main memory, so i would expect a ram test to find the problem and there would likely be other worse OS crash issues. Pretty unlikely that just the memory locations used as video memory would go bad.

I suppose one thing you can try is running some 3D intensive stuff like games or benchmarks. Bad video memory can sometimes cause even worse glitched in 3D.

[Berni]

Alright then. Well one thing you can try is also running at a different resolution or attaching an external monitor (If there is a convenient way to do that on your particular mac). If the same pattern only appears on the built in screen then you know its the display.

[Berni]

That's weird.

Definitely sounds like its a problem in the frame buffer. Perhaps there is a cache in the way that is only being used for graphics? Also possible that there might be a separate video resampler chip somewhere on there that drives the screen and muxes all of the video. But it does sound like you will need some motherboard repair in any case.

If the thing is out of warranty sounds like the best bet is an unauthorized Rossman-ish repair shop.

[Berni]

Well its always possible.

I have done a BIOS update on my Agilent MSO9000 scope that fixed minor display artifacts because the LVDS output to the LCD panel was not configured quite correctly on that fancy proprietary motherboard.

[jc101]

MacOS X update to 12.4.6 today lists a fix for a graphics issue, it says on when waking from sleep but could be related.