If your CPU cooler uses two different headers, you can plug the main one into your CPU_FAN header and the other one into your CPU_OPT header. What is CPU_OPT?Ī motherboard’s 4-pin CPU_OPT (‘CPU Optional’) header is its optional header for plugging in CPU fans. This lets your motherboard see that the CPU is being cooled, and it lets you configure and regulate the CPU’s temperature by adjusting CPU fan speed in the BIOS. This means if there’s no fan connected to the CPU_FAN header, your motherboard will likely think there’s no fan cooling your CPU at all and will prevent you from booting the system.īecause of this, it’s crucial that you have your CPU’s fan plugged into the CPU_FAN header.

Your motherboard should register this CPU_FAN header as the primary one for CPU cooling. What is CPU_FAN?Ī motherboard’s 4-pin CPU_FAN header is its primary header for plugging in your CPU cooler’s fan, and it’s usually located near the CPU socket. It’s usually only when you need to connect multiple CPU fans that you should consider using the CPU_OPT header. The long story short is that you must have a CPU fan plugged into the CPU_FAN header, otherwise your motherboard likely won’t register that there’s a CPU fan connected at all.

It can be disheartening to install one of the best gaming CPUs and a third-party CPU cooler only to find that there are two places to plug in its fan and you have no idea which header to use.Ī CPU fan’s connector can be plugged into either the CPU_FAN or CPU_OPT header on your motherboard-but choose wisely, because having it plugged into the wrong one can lead to your system not booting and your BIOS throwing out errors. Often the most difficult step when building or upgrading a gaming PC is connecting all the power cables.

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