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I think this question has already been answered, but the answer provided is 7 years old. So, I’m not sure if times have changed and that this may be possible now. I have a late 2014 27" 5K iMac with an AMD R9 295x with 4gb. Using a temp sensing app, I notice that the GPU temp while playing games are constantly over 100 degrees C, even with the cooling fan running at 2700 rpms. I checked the air vents at the bottom of the computer and found them to be completely clogged. Using compressed air, I cleaned out all of the vents. Everything (CPU, HD, etc.) are all running much cooler now, but my GPU is still getting over 100 degrees C. I know iMac’s run hot, but it seems that it gets so hot that the computer shuts off. I can play a game for roughly 10-20 minutes and then the computer just shuts down. No error messages. No blue screens. Nothing. Just powers down. I was planning on opening the computer and doing a full internal cleaning and inspecting the heat sink for the GPU (if it has one). I was going to clean and replace the thermal paste and put everything back together. Since I was going to be opening the computer, I was curious if the GPU could be upgraded from the AMD R9 295x. If not, I may just replace it as I do not know if it has been damaged from long term high heat. Anyone have any thoughts about this? Is this a good plan? Am I wasting my time? Thanks for any assistance!
Well your clogged vents are telling you something! Your system needs a deeper clean! I’m sure the heat sink fins and the fan blades are likewise loaded with dust and debris! So I would make the effort to clean things up. As for upgrading the GPU sadly thats not practical! As you can see here the GPU is solder to the logic board (marked in Red)
So your system is one of these iMac15,1 and as well can see the AMD R9 295X is the premium GPU. Update (08/11/2022) An example of TG Pro
