I recently bought a Macbook Pro 15" Retina (late 2013). It's the base model (Intel Iris Pro) and my first mac. Now the issue I'm having is the machine starts overheating while watching Youtube on Chrome/Firefox when the screen resolution is 1920x1200 (scaled-more space). Watching a HD video on Youtube results in temperatures in excess of 90ºC and raises the fan speed to around 5000rpm. 1680x1050 raises the temps to around 75ºC which kicks the fans up to a barely audiable level. 1440x900 is perfectly fine. No issues to report. What's interesting is that watching the same video with Safari produces no such issues... Temperatures don't go over 52ºC and fans run at stock/2000rpm speed. So what is Safari doing differently?