I’m not good at case-modding, and I cannot judge at all whether a cooling system is a good one or not. So I have to totally trust in the engineering power which Microsoft has invested into the Xbox 360 cooling system.
Still, my Xbox #9 had a problem, even I could see that.
I’ve removed the GPU heatsink, and removed the (evil? Probably not really.) thermal foil (I couldn’t see any damage/misalignment on it, though.), and applied some little bit of arctic silver 5 instead (after cleaning the heatsink).
xenon9:~# /usr/src/smc -sso this looks already MUCH better (notice the smaller difference between the 2nd (GPU) and 3rd (EDRAM) temperature!).
sensor data: 55.8 C, 58.0 C, 60.2 C, 29.9 C,
It now matches the cooling performance of the other 9 boxes. (That also means that the arctic silver is as good as the original thermal foil - UNLESS something is wrong with it.)
What worries me more is that this issue didn’t seem to be caused by a miscalibrated or defective sensor - it seems that my change really changed the temperature. That also means that it was incorrect before, possibly overheating.