Random restarts/shutdowns - never when AHT is running!Dear All, I have been struggling with my attempts to fix my sister's iMac 27" mid-2011 (which used to be mine). The problem i...
回复： Random restarts/shutdowns - never when AHT is running!Thanks a lot, Dan - actually I had already done this before reading your advice. Interestingly, the iMac lasted a bit longer whenever booted in Safe Mode - and before that I was able to clean install El Capitan with a USB stick even though the random restarts were still taking place. I also took the opportunity to reset the PRAM a couple of times and install TG Pro. Now the weird thing is: suddenly the iMac stopped suffering from such random restarts even in normal boot mode and with many apps open at the same time, including Youtube on Safari, Grapher, GPU Test and so on (in order to stress the GPU as well). Uptime right now is about 2 hours, something that I could not even begin to consider before. Yet the exact reason is unknown - I am/was absolutely sure that it had something to do with the GPU and/or GFX drivers, or perhaps the PSU under stress - now I am not so sure. Any ideas?