They’re both used for powering additional fans to help with your system’s airflow, and they can both come as either 3-pin or 4-pin variants. FAQ What is a CHA FAN header?ĬHA FAN header, often called SYS FAN header, is a connector on your motherboard used for powering and controlling your system/chassis/case fans. They are in charge of powering system/chassis/case fans and typically come in 3-pin or 4-pin variants. Long story short – CHA FAN headers are the same as SYS FAN headers. These are essentially the same exact thing – they’re used for system/chassis fans and come as either 3-pin or 4-pin variants. Some Motherboard manufacturers use the name “ SYS_FAN” instead of CHA_FAN, but they are essentially the same thing. In this MSI BIOS, the CHA_FAN1 Header would be controlled through the “System 1” tab, CHA_FAN2 Header through “System 2” and so on depending on where your case fans are plugged in to. In the image below you can see how individual fans can be controlled by adjusting their fan curve and choosing the source temperature sensor. The adjustments are based on internal temperature data, either average system temperature or CPU temperature. RPM can be controlled either through the BIOS, dedicated software, or the operating system. They typically run at maximum speed, though can slightly lower it down by lowering the voltage.Ĥ-pin CHA FAN headers have pulse width modulation on the fourth wire which allows direct control over the RPM.

CHA_FAN Headers on an Asus B550 Motherboardĭepending on the motherboard you’re using, you will have anywhere between one and six CHA_FAN headers alongside CPU_FAN and potentially a CPU_OPT header too.ģ-pin CHA FAN headers don’t have the ability to accurately adjust their RPM (rotations per minute).

Asus motherboard fan control