Fan connector confusion

[brianz]

On the Asus P6X58D Premium, there are three fan connectors, each called CHA_FAN1/2/3. However, CHA_FAN1 has 4-pins, while 2 and 3 have 3-pins. Interestingly, the CHA_FAN1 extra pin isn't labeled PWM in the manual, but +5V. What does +5V mean, and what does it imply for choice of fan to connect? Should I connect the biggest fan, the smallest fan, or does it not matter?

All my fans have three-pin plugs anyway, so does it even matter, since I'll have to leave the +5v pin empty anyway?

All three are supported by Asus Fan Xpert so it has nothing to do with fan control, through PWM or through Asus utilities. I'm guessing it means that it supports a bigger fan?

Thanks,
Brian

 

[BonzaiDuck]

BrianZ --

I took a look at the user's manual for the P6X58D Premium at the ASUS web-site.

I haven't worked with these newer motherboards, but I have several with PWM plugs for the CPU_FAN header. It appears that both CPU_FAN and CHA_FAN1 are identical. Note also that they have the "key" or tab which locks to the standard three-pin fan plug, and such PWM headers for CPU_FAN are made this way to accept the standard three-pin fan plug.

I'd be surprised if the CHA_FAN_PWR pin DIDN'T supply 12V to a conventional fan-plug. In other words -- I'm pretty darn sure that it does.

The two four-pin plugs may be labeled differently on the mobo and in the manual, but I don't think there is anything different between them. Someone else may have more specifics in that regard, but I'm pretty sure you could hook up a three-pin plug to fit the tab on CHA_FAN1 and it would supply the 12V and enough amperage to run the fan at full speed. It may even be "controllable" -- despite the fact that the four-pin arrangement accommodates a PWM option.

My limited understanding of PWM (pulse-width-modulation) suggests that it supplies power in increments as needed, while the three-pin control mechanism occurs through continuous voltage variation. Somebody else could correct me on this, but that's my understanding.

 

[harvt5]

this should help people explaining it

here is a pic - the relevant one -from the manual
http://img682.imageshack.us/img682/1287/sdfql.jpg

 

[harvt5]

I don't know..

but i'll just provide some more info..

maybe more questions than answers, but progress.


About PWM
http://www.pavouk.org/hw/fan/en_fan4wire.html
http://www.formfactors.org/developer/specs/4_Wire_PWM_Spec.pdf

Pin Function Wire color
1 GND Black
2 12V Yellow
3 Sense (tach.) Green
4 Control (PWM) Blue


CPU FAN and CHA FAN1, are both 4 pin.. prob both PWM. I am not sure why the pins are labelled so differently in the manual(shown in pic from manual).

I can see why the motherboard may make you think some fans are 5V.. I don't know about that.. or why it doesn't say 12V.. Since from what I've read, PWM has a pin rated 12V not 5V.

I don't know what "FAN IN" is.
And I don't know what all the refs to "FAN PWR" are..
Though "PWR_FAN" would be a connector to do with the fact that some power supplies use that for their fan. (maybe for monitoring of RPM, or maybe for power too)

That's just what I can figure out.. Mostly not things i'm that familiar with.