shamino wrote:

I think you almost definitely have a thermistor inside the fan which is interfering. It's a dumb feature of AMDs stock fans that shouldn't be there, but it is, at least in the K8 and K10 fans I've seen.

Interesting... my guess is they would have those in there in the event that the motherboard itself fails to apply a proper speed signal to the fan, thus preventing it from spinning up as temperature increases. This could explain why the fan speed can increase several hundred RPM over a course of minutes or hours with all the temperatures I can monitor staying still on the high side. The thermistor temperature slowly rises and the resistance slowly drops, allowing the fan to spin faster, yet the thermistor itself doesn't report a temperature so I can't know how hot or cold it is and thus how it's affecting fan speed.

That's also one of those things I don't think a lot of people would really know about. :o

I don't think it's really a safety thing - without a thermistor the fan would run full speed all the time, unless the motherboard supports slowing it down. If the motherboard didn't support fan control, then the hardware would be safe, it would just be louder than it needed to be.

The ironic thing is that AMD only started using these thermistor fans just as motherboard PWM support was becoming near universal. If they had used these fans on the K7 Athlon, then it would have made some sense. But on the K8 and later, they just interfere with the motherboard, which has a far better and faster reading of the CPU temp than that thermistor does. The multi-level power states of the K8 can also make the fan lag a more serious problem than it would have been on the K7, where heat dissipation is more consistent.