3-Pin fans are usually fixed-speed fans, they can however be voltage controlled when the motherboard allows it. Voltage control typically provides lower efficiency than the PWM control, minimum speeds are also not as low as with PWM control.
4-Pins fans can be speed regulated by PWM. This allows a finer control of the fan and allows to reach lower speed for silent operation.
3-Pin and 4-Pin are cross compatible but with some limitations as illustrated in below table.
Plug different fans into the corresponding header. Such as, plug the CPU fan to the CPU_FAN header, plug the case fans to the chassis headers (SYS_FAN/ CHA_FAN)
CPU_OPT header is for second fan of you CPU cooler.
The names of the fan headers will be printed on the motherboard. (please refer to your motherboard manual).
Ensure the fan cable is fully inserted into the header.
If your motherboard doesn’t have enough fan headers, please try our PWM Sharing cable or PWM Fan Hub or PST fans