Controlling Fan Speed

[TheChamp1000]

I currently have 3 fans in my system

AMD Phenom II 940
Biostar TA790GX
Coolermaster 690 case

1 fan is the cpu fan 1 is an exhaust fan and I have recently put a kaze maru 140mm on the side panel of the case.

With two fans CPU and Exhaust the system is quiet enough but I want to add a little bit more cooling without too much noise.

My problem is that the kaze maru fan runs at full speed and I cannot adjust the speed.
I have all three fans connected to the motherboard and I can only change the speed of the cpu fan?

The cpu fan runs quite silent even at full speed so I dont need to change its speed the same with the exhaust fan.

I have tried to use amd overdrive but when I change the fan speed it always changes the cpu fan?
I tried a program called speed fan and the same occurs? both programs show 3 fans available to control but only the cpu fan changes speed no matter what you fan you select to decrease the speed of.

any idea why I cannot change the speed?

[K22]

If the CPU fan is acceptably quiet at full speed, why not plug it into a different header, leaving you with a header which you can adjust to plug your kaze maru fan into.