PWM / Voltage control / 3pin / 4 pin?

[VaderDSL]

Bit confused on the differences on controlling the fans in a new build I'm considering.

First up, looking at a Gigabyte Z170X-UD3

The fan headers are as follows

This is where my confusion arises.

CPU_FAN is fairly self explanatory, from what I understand on this board in particular, that one fan header will read the temperature from the CPU and will adjust the fan speed via PWM, right? It runs the fan at 12v and simply changes the RPM, no voltage changes?

This requires a fan with a 4pin PWM ability, such as is found on most modern heatsinks/fans (in my case a Noctua NH-U12S).

But the SYS_FAN 1/2/3 these are voltage controlled only? On this board there is a temperature probe in the bottom left corner which controls the speeds of these fans.

If I connected a 4pin PWM case fan to these headers, would the fan speed be reported? I assume yes and I believe any changes to the fan speed would not be via PWM but would in fact be changed by the motherboard through voltages instead?

Additionally, if I connected a 3 pin fan to the 4 pin header, I would place it on pins 1-3 which would mean it would run at full 12v but would report the fan speed only yes?

Have I got this correct?

Finally, reading around it has been said that sometimes voltage control on some fans can cause a ticking/clicking noise as the motor responds to the changes in voltage. Any truth in this, and should it be something to be concerned about?

Cheers.

 

[Tealc]

According to that schematic your CPU FAN is PWM only. If it allowed voltage control you'd have 12v/Speed control on Pin 2. You need a 4 pin fan or a PWM to DC converter. You may find voltage control will actually work, it may just be that your manual is pants and not wholly correct.

Sys fan1,2 and 3 look to be voltage controlled only. VCC is probably a 5v signal to engage any 4 pin fans fitted and to make them go 100%. Any voltage control you can with your motherboard will affect 3 pin fans and 4 pin fans similarly.

4 pin fans are better running on PWM as they are not designed generally to run on less than 12v, they can and will run but you may find they stall at far higher speeds than a like for like 3 pin fan would.

Reporting of fan speed will work whether you fit a 3pin to a 4pin header, a 3 pin to a 3 pin or a 4 pin to a 3 pin as they all share the common pin 3.

Ticking is a thing with PWM fans generally although I had a 3 pin fan once which ticked no matter what I controlled it with.