I'm hoping someone might shed some light on this. I just installed a case fan (system fan) that is rated at 2400rpm. I connected it to the motherboard via a 3-pin power connector. The BIOS is only showing it spinning at 1700rpm. I'm going to exchange the fan but I'm curious if it might be some motherboard setting. My motherboard is a Gigabyte EP45-DS3R. If the fan isn't defective is there a voltage setting for fans?

Your mobo in bios is probably set for auto speed control which adjusts fan speed depending on temperature. disable it and it will run at full speed or close to that

^ its a noise reduction "feature"

Personally I feel a lot better knowing the exact voltage that is getting fed to my fans. A simple 7v or 5v mod takes like 30 seconds.

On that motherboard the only auto feature listed is for the CPU fan. There isn't any mention for system fans. Rght now I had this case fan hooked up to System Fan_2 and a Corsair Dominator fan (over RAM) hooked up to System Fan_1. The Corsair seems to run at full speed (it reads 6000 rpm, which is basically the 3 fans running at 2000 rpm I guess) but the 120mm fan which is rated for 2400 or 2500 rpm runs much slower. Also, do people recommend leaving the CPU fan on auto or at constant max speed? I have an Antec P180 case so noise isn't an issue...it is pretty soundproof (with the exception of the Power Supply).

heh, the p180 isnt "soundproof"

well it is a lot quieter than many other cases I've heard.

Can someone also chime in on why my Zalman 9700 won't drop below 2700rpm, even with auto speed control set? My Q9450 is overclocked to 3.2GHz and temps are below 40 at idle. i figured the fan would drop lower than 100% at idle but I never see that happening. I thought it might be a BIOS glitch so I called Gigabyte and they said that overclocking will encourage the need for the fan to always be at 100%, even under 0 load and set at auto. I'm thinking that maybe the Zalman 9700 doesn't support the automatic fan control feature on the motherboard? That's why they include the manual fan speed control device with the HSF?