On my PII 965 in the gaming rig, the motherboard will ramp up the fan to around 2800 by 55 degrees, 4000rpms by 58-59 degrees, and upto 6990 rpms by the time I get to 62 degrees on a very hot day. You’ll usually find your fan controls under options menus titled Cooling, Performance, or CPU. To enter your computer’s BIOS menu, press F2, F12, Delete, or your computer’s BIOS key while booting.

Thubans are safe for temps upto 62 degrees or so, and your motherboard will adjust the fan speed accordingly. You can also make manual adjustments to your CPU fan from your BIOS menu. I would leave your motherboard's onboard cpu fan controller alone to work by itself as it should do a decent job as long as you don't turn it off. I would also imagine that it could decrease the life of the fan, although the fan was designed to spin upto those speeds and shouldn't be damaged. I can't imagine why you would want to run your fans at high speeds all the time as it is loud enough to be uncomfortable. The stock PII cooler maxes out at upto 7000rpms, and you'll know it when it gets that high as it gives new meaning to a 'dust buster.' It is ear piercing deafening loud. That Thuban is just waiting for you to crank up the clocks on it, but you need a very good air cooler first. As others say, I recommend that you go out and get a decent air cooler.

Amd cpu fan control