IP35 Pro - fan speed control not working

[stroberaver]

So Abit finally releases a new final bios for the IP35 Pro to support the 45nm processors. Great, now the mobo can read the cpu temperature, I can use the onboard fan speed controller to reduce the noise of the CPU cooler's fan.

Or not.

The BIOS upgrade went fine - did it from floppy, it took a while but successfully overwrote all the blocks, then tried to reboot, after which point I did the cmos reset and fired her up again, and the bios was fine.

One of the first things I did was check the fan speed controls in the BIOS, and I saw that the cmos reset defaults to having the fan speed control enabled. The cpu fan was only running at 60% of the full speed.

But it doesn't change. Nothing I do in the BIOS or uGuru has any effect on the fan speed. Doesn't matter what I set it to, it just sticks at the same speed no matter what the cpu temperature. At first it was at 720rpm (it's a 1200rpm fan), and these days it's running at full tilt again.

What's more, the cpu temperature sometimes appears locked, usually at 31°C. It's obvious when it's correct, as it idles around 25-26°C, and goes up by about 10°C under load. But other times it's clearly stuck.

Anyone got any suggestions on what is wrong, and how to fix it?