120mm Fan Testing on an MCR120 Radiator Round 6

[jalyst]

PWM is a method of manipulating an electronic signal thru switching the signal on and off while changing the on and off timing, for this context with the illustration below, the top one is at full 100% duty cycle while the bottom one full flat 0% lowest possible duty cycle.

PWM-Duty%20Cycle.gif

Interesting, I THINK I get it now, thanks!

Actually any mid to top class OC-ing mobo should have plenty of fan's header that have PWM control at them, and for sure any new mobo starting from LGA775 generation, at least the CPU fan header already has the PWM capability since the stock cpu fan is 4 wires PWM fan, just look at the header, if it is 4 pins, its definitely capable of controlling pwm fan.

As I suspected,
But it's not just the CPU fan-header, all fan-headers on modern top-end boards are 4-pin nowadays, aren't they?

*edit* no they're not

About hooking up multiple PWM fans, actually you don't need to worry about adding the additional fan controller, if all your fans are 4 wires pwm type, you can drive multiple fans using just single fan header, and control all them from software. All you need is just a simple rewiring at those fan's wires, just re-reoute all pos and neg wires at each fan directly to molex wires from psu, while all the PWM wires from the fans are connected together at the mobo single fan header at the PWM pin.

Why not connect each PWM fan to each of the PWM fan-headers instead of just one PWM header?
I have 2x PWM headers and will probably only have 2x PWM fans, the rest will be AP-15 & 14, which I believe are not PWM.
That way each fan gets power & passes/receives RPM/PWM signals independently of one another.
Of course any fan/s that are too powerful for the mobo's power regulation would need their +/- wires rigged to a molex connector.
And then be connected directly to the PSU, but otherwise....

While for the RPM sensing, these can not be join together, you need to connect each of the fan's rpm wire to every fan headers available at your mobo at the rpm pin if you want to monitor their speed. This is logical since the mobo can not tell which is which, also from the rpm signal characteristic, they just can't be mix together.

Yeah this makes sense, thanks!

If you're using identical fans at the same place say like rad, all their speed should be similar at the same PWM dutycycle, and just pick one of the fan's rpm sensor and use it to represent all others fan's speed.

Wouldn't it be better to have discrete RPM sensing for each individual fan?
e.g. if you have 4 fans on the rad, but all 4 fans are represented by only one RPM sensor, then you wouldn't always know if one fan dies!
I guess that's just the limitation of not having enough headers, sigh, perhaps longer-term I'll need a multi-channel fan controller.