This is known as pulse width modulation (PWM). The remaining fan headers on the motherboard should be CHA_FAN, PUMP, or M.2. These can be used for various parts, depending on what you have to ...

Of course, the standard way of controlling CPU fans these days is with PWM, so he built a circuit which essentially converts the PWM signal from the motherboard into a phantom thermistor.

This hub provides four USB 2.0 headers, supporting up to eight downstream ports with a total output of 2.5 A, and includes six 4-pin PWM connectors, each capable of handling up to 2 A for UNI FAN ...