How exactly does speed fan work?

[Emtiph]

Well I've installed two case fans and downloaded and installed speed fan but when i adjust the speed the fan speed doesn't actually decrease - it just stays the same. I fiddled about with a bunch of things and nothing seemed to be able to alter the speed of my case fans. What's wrong?

 

[slicessoul]

http://www.almico.com/speedfan.php

At the lowest level, SpeedFan is a hardware monitor software that can access digital temperature sensors, but its main feature is that it can change fan speeds (depending on the capabilities of your sensor chip and your hardware) according to the temperatures inside your pc, thus reducing noise. Several sensors, like Winbond's and the AS99127F support fan speed changing, as well as others from Maxim, Myson, Analog Devices, National Semiconductor and ITE, but the hardware manufacturer must have connected the relevant pins to some additional, yet trivial, circuitry. This means that if you have, say, a Winbond W83782D on a BP6 then you're ok, but not every motherboard with such a hardware monitor chip will be able to change fan speeds.

 

[jt001]

As the above poster says, it doesn't always work. I've had some boards where all the fan headers supported fan control, some where none do, and the board currently in one of my machines supports it on only 2 out of the 3 headers. It's pretty much hit or miss.

You can try switching your fans to different headers, maybe one of the other ones supports it, but it's not likely. In my experience the CPU one is most likely to support it, for obvious reasons.