iMac 5k late-2014 graphics issue

[amenityelk]

hi all,
I just experienced a weird graphics glitch—I was working as normal, when suddenly my screen went black and appeared to cycle between turning on (backlit) and turning off (completely black). Video attached here.

Looking in Console, I found several kernel reports involving the GPU all timestamped at the time at which this happened. I attached one of the seven here.

More info: I recently opened up the iMac to replace the spinning disk with an SSD, several weeks ago. First issue I've had since that time, not sure if it's related...?

I wonder if this has happened to anybody else before?

Thank you!

 

[casperes1996]

Is the GPU the R9 M295X?

I didn't have this particular issue, but my GPU overheated several times to 110C to the point that the entire computer shut off to preserve its life and eventually it clicked and it was completely dead.

And I've seen quite a few others with issues with the R9 M295X, especially in combination with the 4790K CPU.

 

[chscag]

Is the GPU the R9 M295X?

According to the kernel report it's a R9 M290X. But I'm wondering if the fact that the OP recently replaced his drive with an SSD has anything to do with the GPU reset he's experiencing?

That model iMac uses a temp sensor on the hard drive which either needs to be compensated for or bypassed when the drive is replaced by an SSD.

 

[amenityelk]

Yes, that's right—R9 M290X, and the CPU is indeed i7-4790K. Sorry for not including that.

I do have an OWC temp sensor affixed to the new SSD and generally I haven't noticed any difference in fan speed compared to before the upgrade. According to iStat Menus, the GPU die seems to be hanging out around a balmy 110°F, but I'll keep an eye on it.

I also had a thought that it could be the data cable feeding the display—I feel pretty confident that I reattached the data cable properly/securely, but I wonder if that could have something to do with this...?

 

[chscag]

I also had a thought that it could be the data cable feeding the display—I feel pretty confident that I reattached the data cable properly/securely, but I wonder if that could have something to do with this...?

It could be, but it's always a pain to have to open it up again and check. However, that's probably what you're going to need to do. Be careful with the sealing tape as I have seen several incidents where the display fell off because of bad sealing tape.