Are fans connected to the Mobo controlled by PWM?

[Starscream02]

Hi

I built my PC a few months ago and at the time had some crappy 80mm fans lying around. I installed 2 of them in the top of my case to exhaust the hot air. The fan cables were too short to reach the 3 pin connectors on the Mobo, so I had to connect them directly to the PSU.

They are now irritating me because of the noise they make. I am about to purchase 2 good quality 120mm Fans. If I plug them directly into my Mobo, will their speed be actively controlled via PWM (I have seen some fans which state they are PWM but I cannot see any difference between them and the ones I am planning to get)?

If there's no difference between pluggin them into the Mobo or connecting directly to the PSU, then I also won't bother getting a 3 pin fan extension cable (that i would need to connect to the Mobo).

Thanks

Sumeet

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Coolermaster Centurion 590 Case
Coolermaster M620 PSU
Intel Core i7 920
Asus P6T SE MoBo
GSkill DDR3 Triple Channel 6GB 1333Mhz
Samsung 750GB HD
Sapphire 4870 512Mb Graphics
LG 1080p Monitor
Logitech 2.1 THX Speakers
Microsoft Laser Desktop 3000
Window Vista Ultimate 64Bit
Virtualbox Ubuntu 8.10 VM

 

[Special K]

If your mobo has any 4-pin fan headers, these will be PWM controlled. If the fan headers only have 3 pins, then they are not PWM controlled, although you might still be able to vary the fan speed by varying the voltage.

Also keep in mind you will need to buy fans specifically designed for PWM. Here is the PWM fan I use with my HS:

link