3pin vs 4pin pwm for CPU

[Bramm17]

Hi all,

 

Dunno but maybe the supidest question you have ever seen but I was wondering what is the difference bewteen a 3pin and a 4pin pwm fan as a CPU fan.

Currently im running a CM Hyper 212 Evo and that has a 4pin pwm fan connector plugged into the mobo. But I recently got a Noctua NF-C14 from a friend and noticed that that one only has a 3pin fan connector. Since I was planning to switch my Hyper 212 for this NF-C14 I was wondering what the difference between this 3 and 4 pin was and if you guys recommend the upgrade?!

 

Thank you :)

[extremescouter]

I believe the extra pin allows you to control the fan through your motherboards software, or through other software. The fans only need 3 pins to work, but the extra pin is there for enabling fan profiles and such. 

[Dave :)]

As above - the fourth pin is what allows for "PWM", basically allowing you to change your fan speed.

[bennyino]

i believe 4 pins allow for control through speed, 3 pins through voltage and 2 pins allow no controll, unless you are using a fan controller

[Hyydrah]

You can still change your fan speed with a 3 pin fan header. 4 pin fan headers simply provide better results (can eliminate clicking noise, for example).

[Mooru]

A 3 pin header controls the fan speed using a constant voltage. This has one big disadvantage. Most fans need a minimum voltage to start spinning. Let's take as an example 5V. If you want your fans to spin really slowly and you set them on the lowest setting it is possible they'll receiver a lower voltage, and won't even start spinning (especially true with a fan speed reducer, tried this with some crappy noisy fans in an attempt to make them quite).

 

A 4 pin header uses PWM to control the fan. This kind of controller will send a pulse of 12 volts to the fan and afterwards turns the output to 0 volts again. This means that the fan will start spinning due the maximum volts applied. But while the voltage is 0, the inertia of the fan will keep it spinning for a while. To increase fan speed, longer pulses will be applied and the 0 volts won't last so long. In general this method can give much better control results and lower rpms. Life span of these kind of fans could be lower, but in todays world with quality components this is hardly an issue anymore.

 

I hope my technical rant is a bit understandable.

PWM is alot easier to understand with a drawing.

Google is your friend :)

[ProGearUk]

The extra pin should control the fan speed better and make things a bit quieter.