Today, I reset the BIOS with the pinhole switch, now my 6600H is running hot and the fan is audible. CPU temp is about 46 degC whereas before it was in the 30s. This did not happen with previous BIOS resets.
I am running Fedora Linux. In previous tests I found that the 6600H actually ran cooler under no load when I set the total power BIOS setting to 45W vs the default 35W, perhaps because the OS was able to control the CPU state more effectively. So that is the only non-default change I currently have in effect.
The fan now makes a sort of rattling sound. Since it’s been a while since it ran at full speed, maybe there is dust in the fan that is reducing it’s effectiveness.
Any other ideas?