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CPU OPT vs CPU FAN – What is the Difference?

When constructing or upgrading a gaming PC, connecting all the power wires is frequently the most challenging task. Installing one of the top gaming CPUs and a third-party CPU cooler might be frustrating when you discover that there are two spots to plug in the fan and are unsure of which header to use.

You can attach a CPU fan’s connector to either the CPU FAN or CPU OPT header on your motherboard, but be careful which one you pick because doing so could prevent your system from booting and cause your BIOS to issue errors.

To cut a long story short, if you don’t plug a CPU fan into the CPU FAN header, your motherboard probably won’t even recognize that a CPU fan is connected. The CPU OPT header should typically only be used if you need to connect several CPU fans.

What is CPU FAN (CPU_FAN)?

The 4-pin CPU FAN header, which is typically found next to the CPU socket, is a motherboard’s primary header for connecting the fan of your CPU cooler. This CPU FAN header need to be recognized by your motherboard as the primary one for CPU cooling. This implies that if a fan isn’t attached to the CPU FAN header, your motherboard will probably assume that there isn’t even a fan cooling your CPU, which will prohibit your computer from booting.

It’s essential that you wire your CPU fan into the CPU FAN header as a result. This enables you to configure and control the CPU’s temperature by adjusting CPU fan speed in the BIOS and enabling your motherboard to perceive that the CPU is being cooled.

What is CPU OPT (CPU_OPT)?

The CPU OPT (‘CPU Optional’) header on a motherboard is an optional header used to connect CPU fans. You can connect the primary CPU cooler to the CPU FAN header and the secondary CPU cooler to the CPU OPT header if your CPU cooler has two distinct headers. If there are more than two headers, you can combine them using a splitter and connect the other ones to the CPU OPT header using a single wire.

CPU OPT is mostly used to connect cooling systems with numerous fans or to power AIO cooling pumps when the motherboard’s AIO PUMP header cannot be used. Your system should boot without anything hooked into this port. Just be aware that if the AIO pump is connected to CPU OPT, the BIOS won’t allow you to alter its speed.


CPU fans can use either the CPU OPT or CPU FAN headers, but only one of them is “optional,” as the names imply. If a fan isn’t connected to the CPU FAN header, your motherboard might assume there isn’t one cooling the CPU and won’t allow you to boot.

For additional CPU cooling connectors, such as those found in a multi-fan radiator configuration, CPU OPT should be used. If you can’t connect it to the proper AIO PUMP header, you may also use it for an AIO’s pump, but you won’t be able to regulate the pump speed from the BIOS. If SYS FAN or CHA FAN headers are not present, you can also connect case fans to CPU OPT, but the speed of these fans will only be controlled by the temperature of the CPU rather than the entire system.

Can You Use CPU_OPT for Case Fans?

Although the CPU OPT header can be used for case fans, it is not advised to do so when the SYS FAN or CHA FAN headers are available. CPU OPT, like CPU FAN, is only connected to the temperature sensor of the CPU; it is not connected to the temperatures of the system as a whole or of other components. As a result, if you connect a case fan to the CPU OPT header, you won’t be able to control its speed according to the temperature of the entire system; instead, it will only be controlled by the CPU’s temperature. On the other hand, you can connect a case fan to CPU OPT if your motherboard’s SYS FAN or CHA FAN headers are all used up.