Chassis fans, DC vs PWM mode

[eco_bach]

So the chassis fan connectors on my ASUS X98All support both DC and PWM modes. But I'm confused by the difference and which to use. Can anyone clarify?

 

[ehume]

PWM headers will run 4-pin PWM fans or 3-pin voltage-controlled fans.

Case fans usually run at 100rpm to keep the noise down. Heatsink fans usually use PWM controls to run their speed up & down to accommodate the demand placed on them.

A case mfr that makes case fans PWM is either forward-thinking or market thinking. If it is AS.S it is the latter.

 

[batboy]

PWM fans are controlled by temp. The hotter it gets, the faster RPM the fan runs.

 

[EarthDog]

This thread... wow....cleaned up useless posts...

PWM fans are controlled by temp. The hotter it gets, the faster RPM the fan runs.

No, that isnt true. They CAN do that, but so can DC controlled fans. They are 2 different ways of controlling speed. One is by voltage (the more volts the faster) vs PWM which adjusts the modultaion of the voltage....voltage stays the same but the frequnecy of voltage and no voltage controls the speed...

https://www.ekwb.com/blog/what-is-pwm-and-how-does-it-work/

Case fans usually run at 100rpm to keep the noise down.

im sure you meant 1000 RPM.