CPU_OPT Vs CPU_FAN Headers: How Are They Different And Which One To Use For The CPU Cooler?

Dealing with the labyrinthine mess of wires and motherboard headers is one of the more tedious — and sometimes downright frustrating — aspects of building a PC, in my opinion. It’s a tedious dance of tiny pins, microscopic wires, and frustratingly tight spaces. And if that’s not enough, you’ll also find yourself deciphering cryptic and infuriatingly similar labels on the motherboard most of the time.

The CPU_FAN and CPU_OPT, for instance, are two very similar headers you’ll find on most motherboards these days. If you ever find yourself in a pickle, trying to identify and figure out which one to use, then read on to find out which header to connect your CPU cooler and case fans to.

Related

5 features to look for in a new motherboard

Planning to buy a new motherboard? Here are some quality-of-life features you should keep an eye out for

Which one to connect your CPU cooler to?

The CPU_FAN header, which is often labeled as CPUFAN or CPU_FAN1, on the motherboard is a four-pin fan header that can be used to both power and control the CPU cooler that’s installed on your PC. This particular header is typically found either on top or the right-hand side of the CPU socket. It’s a universal header that can be found on pretty much every motherboard out there, and it can use a technique called pulse width modulation (PWM) to control the fan speed dynamically based on the CPU temperature or based on the fan curve you’ve set.

CPU_OPT, which stands for “CPU Optional” and is often labeled CPU_FAN2, is also a four-pin header that’s similar to the CPU_FAN header we saw earlier. You’ll typically find this particular header either next to or beneath the CPU_FAN header, and it’s an “optional” header for those using aftermarket coolers with more than a single fan, like the Noctua NH-D15. It’s worth pointing out that the CPU_OPT header on some cheap motherboards only has three pins, meaning it lacks PWM fan control.

While both headers essentially solve the same purpose and can power your CPU fans, it is recommended that you connect the CPU cooler to the CPU_FAN header, not the CPU_OPT. I say that because in many cases your system simply won’t boot if there is no connection to CPU_FAN. It’ll throw a warning at the very least if there is no connection of CPU_FAN, and that’s probably something you wouldn’t want to deal with later on by heading into the system BIOS. The CPU_OPT doesn’t check for a connection before booting the system, meaning you can leave it as it is.

Use CPU_OPT for a secondary CPU cooling fan or system fans

The optional header, as the name suggests, is better to be used with the secondary fans that ship with aftermarket coolers. You may not get PWM functionality depending on whether it has three or four pins, but it’ll still work as long as you control the fan speed manually. Alternatively, you can also use the CPU_OPT header to power additional case fans to maximize th airflow within your system. You can opt for case fans with either three or four pin headers, or you can even use a Y-splitter on the CPU_OPT header, as long as your motherboard can handle the power load.