UPDATE: it is working great now, it was the disconnected display that caused the high CPU usage. ============== I did the upgrade and the performance is very poor. The fan is running at all times and the Kernel CPU usage is very high. I wonder if the problem it is not enough cooling or if it something else got damaged. This is for a Late 2012 iMac 21.5” 2.7 GHz (originally). I’m tempted to go back to my old processor.