3 pin and 4 pin - Help?

ShivP

ShivP

ShivP

Soldato
Soldato
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Hi,

I have a couple of PWM (4-pin) Arctic F8 PWM Fans in my PC and they work just fine, can control them through speedfan no problem. Now, my brother has two non PWM Arctic F8's plugged into 4-pin headers on his motherboard and they work in pretty much the same way as mine - therefore, what's the difference? He can control them as I can through speedfan, and that seems to be the only thing that we need them to do, so I'm unsure as to what the PWM (4th pin) is actually for - does anyone know? Looking into getting an AF120 and wondering if it's worth spending the extra for the 4-pin over the 3-pin fans.

Cheers,

Shivy011
 
PWM allows you to control the fans using a signal which tells the fan how fast to run.

non-pwm fans are controled by how much voltage is fed to them (i.e. 4v=600rpm to 12v=1200rpm for example)
 
Just go with the 3 pin, PWM is the norm for fans used on CPU coolers due to them being able to be automatically controlled according to temperature
 
Not all motherboards control 3 pin fans very well but they'll all control PWM fans.

PWM is a digital method of control and can generally drive fans at a lower speed and with a finer level of control than DC regulated voltage. It can also be more efficient and produce less heat as for a percentage of the time the fan is effectively switched off.
 
Ok, so the only major difference is that the pwm fans can stop making the pc quieter and that's about it?
 
pwm are usually quitter due to them ramping down when pc is idling

non pwm will run at a constant speed no matter what unless you hook them up to fan controller or slow them down with software
 
Ah, that's why speedfan works. Looks like ill go 3 pin to save the extra couple of quid then.
 
Does anyone here know how the Akasa two-way fan splitter cable works because I'm still unsure whether both fans need to be PWM compliant?

The splitter has one 4-pin and one 3-pin fan connector. The information you can find out there is that the PWM fan connected to the 4-pin plug controls the PWM and so syncs the second fan. The two fans effectively are being seen as just one.

As I understand it, PWM works by providing a constant voltage from the header which is being pulsed on and off to control the fan speed with reference to MB temperature sensors. But what about the second fan on the 3-pin plug?

If the voltage is being controlled by the PWM data from the 4-pin fan does the second fan need to be PWM compliant too? If yes, please explain why and what would happen if you used a non-PWM fan.
 
Not sure what cable you are talking about. Unless the cable has some conversion electronics any attached 3 pin fan will just run at 100% as it'll see 12v constantly.
 
I see all PWM 3/4 pin connectors on there, no standard 3 pins at all. This is what is referred to as a PWM splitter.

You can fit 3 pin fans to it as that's the way the connectors are designed but they'll run at 100%, unless you can reduce the 12v by some other means.
 
Tealc said:
You can fit 3 pin fans to it as that's the way the connectors are designed but they'll run at 100%, unless you can reduce the 12v by some other means.
Click to expand...

There are some manufacturers (like Asus) that support both voltage and PWM control on their 4 pin fan headers.
 
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