PWM Options

[Relentless81]

Hey

Just trying to understand something and was wondering if someone could help

My OEM fan is PWM as it has a four pin connector, in my BIOS the CPU fan speed has three options

Auto
Voltage
PWM

As default it was set to Auto, i've now set it to PWM, I thought PWM was the norm these days so i'm a little confused as to why it was set to Auto from the factory and what the difference between the two settings are, anyone know?

Should Kool & Quiet also be on? Its either on or set to Auto as default I cant remember now

Thanks

 

[twist3d0n3]

auto will presumably detect if it's 3-pin (voltage control) or 4-pin (pwm).

cool & quiet will adjust the fan speed depending on temperature, so yeah stick it on

 

[Relentless81]

Ah yeah auto makes sense, i've set it to PWM though and cool (or kool however AMD state it) & quiet was on as default so thats fine but one thing I ont understand is how PWM and Cool & Quiet work if they are both on

 

[Tealc]

I thought Cool and Quiet was AMDs idle CPU speed throttling and power saving technology where the CPU underclocks itself when the PC is doing nothing.

PWM fan control is not really related to this apart from the fact that the fan might run with a lower duty cycle when underclocked due to everything being a bit cooler.

 

[Hagar]

PWM switches the fan motor on and off at a frequency to provide a speed less than the normal constant 12V speed. Uses 12V at the fan. Speed varies with predetermined settings for CPU temperature.

Voltage setting will just vary the fan voltage typically 8V to 12V with temperature on the CPU, useful for three pin fans without PWM

Auto decides between the above based on fan type.

andy