Answer to "Apple STUMPED - iMac shuts off randomly, daily to multiple times/hour"I know this is an old thread but I’d like to share my experience. I had a very similar problem where my iMac would shut off randomly. Turns out the RAM was bad, I replaced the RAM and have been stress testing the machine for four hours using the “yes > /dev/null command and GPuTest. So far so good. Be sure to try removing RAM sticks as part of your trouble shooting process. By the way, the RAM is Crucial 1333MHz 4GB x 4 sticks.