You're welcome. Some more detail (in case you want to know) about how these work. An older 3-pin fan has three connections: Pin #1 is Ground, Pin #2 is the +VDC power supply, and Pin #3 is the speed signal. The Voltage on Pin #2 is varied by the mobo header to control the fan motor speed, from +12 VDC for full speed down to +5 VDC for minimum speed without stalling. The speed signal on Pin #3 is a series of 5 VDC pulses generated by the motor (2 pulses per revolution) and sent back to the header for counting. The header can only deal with the speed pulse train from one fan, so you cannot connect several fans' speed signals in parallel to one header.
There are now two dominant fan motor types called 3-pin and 4-pin for their connection systems. The connectors for both are very similar mechanically and electrically so that you can plug either fan type into either mobo header type, and they will work with a few limiting notes (see below).
The newer 4-pin fan system has slightly different signals. Pins 1 to 3 are almost the same, except that Pin #2 now provides a fixed full +12 VDC power supply, not variable. The added Pin #4 carries the PWM signal. This signal at 5 VDC max is like an old square wave in that it is either fully on or fully off. It is a bit different, though, because its "% On Time" varies, whereas a square wave is on exactly 50% of the time always. Inside the fan motor there is a small chip that uses this PWM signal to modify the flow of current from the fixed 12 VDC supply from Pin #2 through the motor windings to achieve different speeds.
It is now very common for all mobo fan headers to have 4 pins, but what those do can be changed as a configuration option in BIOS Setup for that header. In PWM Mode it acts as a 4-pin header putting out all four PWM Mode signals (including the PWM signal and a fixed +12 VDC supply). In Voltage Control Mode (aka DC Mode) it puts out the older 3-pin signals including a VARYING +VDC power on Pin #2 and NO PWM signal on Pin #4. Thus you can use either type of fan on any mobo header as long as you configure that header for the fan you plug in, AND as long as you do not mix fan types on one header. If you encounter a 3-pin header on a mobo, it can ONLY operate in the older 3-pin mode since it cannot send out any signal on a non-existent Pin #4.
What happens if you mis-match fan type and signal type? If you plug either type of fan into a 3-pin header or a 4-pin header using Voltage Control Mode, that fan receives a varying Voltage supply on Pin #2 and NO PWM signal. On older 3-pin fan is fine with this, of course. A new 4-pin fan gets no PWM signal so its chip cannot modify current flow, BUT the power supplied on Pin #2 is a Voltage that is reduced for slower fan speeds, so that motor's speed IS controlled this way, even if not in exactly the ideal manner. If you are using a 4-pin header operating in the new PWM Mode, the 4-pin fan is fine with that. A 3-pin fan connected there will receive a fixed power supply of +12 VDC from Pin #2 at all times and does not get (could not use it, anyway) the PWM signal. So it runs full speed all the time. You get good cooling this way, just no ability to reduce fan speed.
If you use a SPLITTER to connect several fans to one header all the fans will share the signal set put out by that header. You can use a 4-pin Splitter for either fan type - it only passes the header's full signals (of whichever Mode) to all its fans. The only power source for all the fans on the Splitter is from Pin #2 of the mobo header, and typically that is limited to a max current of 1.0 A.
If you use a HUB to make that connection, the Hub does something different. It gets power for Pin#2 for ALL its fans directly from the PSU via a third connection arm, and it draws no power from the mobo header. This avoids the header's max current limit. The PWM signal from Pin #4 of the header is shared to all fans but this is not a load limit situation. BUT the ONLY power source for all the fans is the fixed +12 VDC supply from the PSU so this device can NOT control the speed of any 3-pin fan. Thus 3-pin fans can only be used with SPLTTERS if you want speed control.
As I said in a previous post, any Splitter or Hub will relay back to its host mobo header the speed pulse signal from only ONE of its fans using Pin #3, and will ignore the speed signal from all other fans. All other signal lines are shared to all fans, so they get exactly the same control signals.
We speak of "speed control" of the fans by mobo headers. That header is not trying to achieve a particular speed. In fact, it does not even use the speed signal for its control functions. It really is a TEMPERATURE control system. The header gets a temperature measured by a sensor near the hot device (either inside the CPU chip, or on the mobo) and alters the speed signal it sends to the fan to achieve a target measured TEMPERATURE at that sensor. It will change the speed signal to whatever it needs to get there, but it does not care or even know what that speed is. So why do we have a speed signal? One is just to inform you, the user. The other is a protection function in all fan headers. It monitors that speed for failure as detected by NO speed (or, in some cases, a speed less than a user-specified minimum) and will pop up on your screen a warning that a fan has failed so you can take action. In many mobos the CPU_FAN header does more that that. Failure (i.e., no fan speed signal) may cause it to completely shut down your system shortly after issuing the on-screen warning to prevent possible damage to a CPU with no cooling. Further, it may not allow you to boot up if the CPU_FAN header cannot detect a fan speed at start-up.
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