I'm quite confused, as in iStat there are 2 temperature readings for the GPU, a 'GPU' and a GPU Diode'. Whenever I do graphics intensive tasks, both GPU temperature values rise as the GT650 is being used. This makes me assume that the two temperature sensors are both on the dedicated GPU (GT650) and not the integrated GPU (HD4000). What confuses me is that if I watch youtube videos, which still uses the HD4000, the temperature readings of 'GPU' and 'GPU Diode' still rises. What does that mean? GT650 is turned on when I watch youtube? BTW, is it normal for the GPU to heat up to ~55 Celsius while on youtube?