4 pin PWM y splitter with different fans and pin layouts

[tibbee1996]

I'm looking for an explanation, and theory that how a 4 pin PWM Y splitter would work with
different
type of fans with different pin layouts in a 4pin connector on the motherboard.

The splitter has two end one with 4 pin and another with 3pin. I know that one of them is only 3 pin, because the splitter need to know only one fan speed , and controll both fan based on that.

But, how you controll a 4 pin and a 3 pin fan?
Because the 4 pin connects perfectly (gets 4pin from splitter),
but the 3 pin fan only gets 2 pin from the other head of the splitter.

Will the 2 fan stay on the same level of rpm, or differ in some level?
Does two different brand cause conflict?

I also interested in two 3pin fan with a 4pin splitter.

Please do not answer if it works or not, rather how will it work.
I am not an expert in thic topic, but rather curios about how fans will behave.

 

[clutchc]

3-wire fans have their speed controlled by varying the voltage; usually from +5V to +12V. As a result, LED lights on those fans will dim and brighten as the fan speed increases/decreases.

4-wire (PWM: Pulse Width Modulation) fans have their speed controlled by varying the length of time the DC voltage is applied (the pulse), maintaining a constant +12V. LED lights on those fans will stay bright when the fan speed increases/decreases.

The missing pin on some 4-wire splitter is the tach wire. The BIOS needs to see only one tach signal so that it isn't confused with competing signals. As a result, it is best to use matching fans on a spliter so you can assume the 2nd fan is running at the same RPM as the first. Using mis-matched fans will cause no harm, but you will not have any idea of the actual RPM of the 2nd fan.

Some motherboards BIOS/UEFI will allow both types of fans to be speed-controlled when plugged into a 4-pin header. Some however do not. In fact, most I have worked with do not. 3-pin fans will then always run at full RPM.

 

[tibbee1996]

Thank you, and sorry for the late response.

Currently my rig has 6 case fans in it. All of them are connected with 4pin splitters into the remaining 4pin connectors on the motherboard.

I will try to describe the observed behaviours on the fans.

Here are the layout of them:

• 
  Back and Top Fans: 4pin-4pin same type
  Side panel and Bottom Fans: 3pin-3pin same type (one has red led)
  Front 1 and Front 2: 4pin-3pin different type

What i saw when messing around in SpeedFan, that the Side and Bottom fans are not visible at all, but working.
Furthermore it seems that the Front fans speed manipulates the Back and Top ones speed propotionally.

What i mean that i cannot change the Back and Top fans speed, but when i change the Front fans speed, they changes with them.
It doesn't seem that i can manipulate the Side and Bottom fans speed in any way.

This way of operation of the fans are not bad, but unpredictable.
I'am really curios why they working so awkwardly, because i expected many scenarios, but nothing like this.

Any ideas?

And again sorry for the late response.

 

[clutchc]

I would suspect it is the effect of the board's BIOS/UEFI, the mix of voltage and PWM control, and the software (Speedfan) not playing nice together. Not knowing what motherboard make/model/version/revision you have, that is about all I can come up with.

 

[tibbee1996]

I've got an Asus M5A97 evo r2.0.
What you're saying could be the problem, still it's the weirdest type of controlling i have experienced in my life.
But it's not that bad, considering that the main intake and exhaust fans can be controlled in some way, so the case cooling works.

In the future i will buy some fans with 4pins and same brand, and then see if that behaviour gonna change or not