PWM or not?

Myranda

Myranda

Myranda

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22 Apr 2012
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Have a Corsair 350D that I want to cool as quietly as possible.

Long term I'd love to water cool it, but between rads and waterblocks I've not quite got the money yet... so for now fans only.

Now, my motherboard has a pile of 4 pin PWM headers so I thought PWM fans...

Is there a disadvantage to this?
 
The only thing you'd miss is manual control. Some like to manually control their fans. Personally I just can't be bothered and would rather let my PC worry about adjusting the speed based on real temperatures of the CPU and GPU.

Oh and I suppose that without a PWM to 3 pin converter you'd be limited to PWM fans. Some of the best regarded are not 4 pin PWM.

Also you may also have a load of 3 pinners that could be put to good use.
 
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As for 3 pin fans...

I've got 3 - one very very dusty inside and I can't get the fan off to clean it, one 140mm VERY noisy fan and 1 good 140mm one.

So looks like I've not got an abundance of spare fans to put to use... seems time to make a fresh PWMy start to things
 
Make sure all those 4pin headers are actually PWM. Many motherboard have 4pin headers that do not have PWM signal on 4th pin.

The solution if using more fans than PWM headers is PWM splitters with Molex or Sata power socket. Using these allows you to have more fans using PWM signal without powering the fan from motherboard because of the molex/sata socket powered directly from PSU
 
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How would one know?
Click to expand...

The motherboard manual would be the best place to check.

It'll look something like

Pin 1 Ground
Pin 2 +12v/Control
Pin 3 Sense
Pin 4 Control

If its..
Pin 1 Gnd
Pin 2 +12v/Control
Pin 3 Sense
Pin 4 Reserved

..then it isn't a proper PWM control output as it needs Control on Pin 4.
 
It's written slightly differently (is Asus so Koreans might label pins in a slightly different way?)

Chassis fans:

Pin 1 Ground
Pin 2 CHA Fan pwr
Pin 3 CHA Fan in
Pin 4 +5V

CPU fan:

Pin 1 GND
Pin 2 CPU Fan pwr
Pin 3 CPU Fan in
Pin 4 CPU FAN PWM
 
The chassis fan looks like an always 100% connector, suggested by the +5v on Pin 4 which is what a PWM signal will look like at 100% duty cycle.

The cpu fan is controllable.

So you might need to look at PWM splitter and have everything running off your CPU fan signal. Most graphics cards also have a valid PWM signal which you can tap into but would need a PH to 6471 connector converter for that.

I guess motherboard manufactuerers still expect everyone to be buying into fan controllers.
 
Though I can adjust min and max speeds of the chassis fans within the bios... surely if the voltage were a constant non-adjustable amount I would only be able set a speed or a voltage... but instead I can set variable speed ranges which react to thermal changes.
 
That is voltage control not PWM control. Meaning all fans running on that header are being powered by that header.

With PWM controlled fan header using a PWM splitter with molex/sata connecter plugged into header the power is supplied directly from PSU.. no load on motherboard header because it is only supplying the PWM signal.
 
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Some motherboard have headers that can be set to PWM control or voltage control.

With a CPU_fan header that is PWM:
* If you plug a fan into CPU_fan header it is PWM controlled and powered by header.
* If you plug a PWM splitter without molex/sata socket into CPU_fan header it is PWM controlled and powered by header.
* If you plug a PWM splitter with molex/sata socket into CPU_fan header the fans are controlled by motherboard and powered by PSU

I edited original post too. ;)
 
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All PWM enabled headers provide power to whatever you hook up to it. The pin 4 PWM switches the fan on and off at 25kHz so it effectively goes slower.

Some splitters are header powered, some are not. Ones that control 3 or more fans tend to use a molex or Sata for power.

Voltage control is often available on non PWM connectors but they give 4 pins so any fan will fit. Nothing wrong with voktage controlling a 4 pin PWM fan really either but a bit of a waste.
 
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