Just wondering anyone experience this with their Retina iMac? It only seems to happen when it is in sleep mode. When I'm using it, no fan noise only time there is fan noise is when I play games on it. I'm just checking to see if this is an issue or problem that's due to hardware and needs to be fixed. I have the i7 with the AMD m295x and currently beta testing El Capitan. Any help would be greatly appreciated.