When you look at your computer’s motherboard, you may notice a CPU OPT one close by once you find the CPU FAN header. Although at first glance its meaning is clear, its exact function can be a complete mystery to new hardware enthusiasts. Let’s demystify that CPU OPT header and explain how it works and what it does!
What Is CPU OPT?
The CPU OPT header in your motherboard is an extra port for unique accessories that you may want to add to your processor’s cooling unit. You’d usually use it for specialized coolers that use multiple fans or water-cooling setups.
Functionally, CPU OPT is the same as CPU FAN, providing a 12-volt DC connection at a minimum of one amp. A CPU cooler manufacturer will require this device connection to ensure that it gets enough power through the entire system to cool the chip adequately.
CPU OPT vs. CPU FAN
Despite their almost identical function, there are a few key differences between these two headers. See below for a quick summary.
| CPU OPT | CPU FAN |
|---|---|
| Your system doesn’t check whether this header has a connection before booting. | Your system will throw an error and completely fail to boot if there’s no connection here. |
| It only provides power to the component connected to it. | It both provides power and communicates with the BIOS/EFI system in your motherboard to provide statistical data. |
| You can connect multiple devices to CPU OPT by using a splitter or hub. | CPU FAN requires that only one device – the cooler itself – be connected to it. |
In short, if you have a CPU cooler, its primary connection should always be CPU FAN. Otherwise, you risk damaging the integrity of your system, and your motherboard will definitely refuse to boot the system. In many cases, it may refuse to go anywhere past the power-on self-test (POST).
Also helpful: there’s much more involved in PC airflow than CPU fans. Learn the ins and outs of intake and exhaust fans to better protect your desktop PC.
Is CPU OPT Necessary?
CPU OPT is a very important part of your motherboard’s ecosystem, compartmentalizing between primary and secondary cooling equipment. This gives you the room you need to experiment with things like splitters and even some case fans, as long as everything you connect to it requires less than one amp altogether.
CPU FAN should only be used for the “main” cooler fan, and that’s it. Don’t attach anything else there!
What About Splitters?
Since most splitters available online do not tell you which fan header they should be connected to, it’s easy to assume that CPU OPT isn’t needed on your motherboard and that you can just put a splitter on CPU FAN.
However, this can lead to unwanted system performance. Splitter cables for fan headers add another point of failure in a system where a lot can go wrong already. The cooler could have improper thermal contact, the fan could be improperly connected, or the cooler could be defective.
You’d have to spend extra time diagnosing these issues if you add a splitter on top of everything else that’s between the CPU FAN header and your chip (e.g., Thermal Paste -> Cooler contact -> Fan -> Fan cable -> Fan connector -> CPU FAN header).
Tip: if you notice your PC isn’t performing well, you may want to cool down your CPU, as it could be overheating.
Can I Use Case Fans on CPU OPT?
Absolutely! As long as everything connected to the CPU OPT header draws less than one amp of power (most powerful fans use about 0.3 amps), you can connect whatever you want to your heart’s content!
Just check how much amperage each component requires for normal operation, and ensure that it adds up to less than your 1-amp budget. Some motherboards will put more amperage through CPU OPT than CPU FAN, so check your motherboard’s manual to see whether you have some bonus allowance you can take advantage of.
In addition to this, you could opt for a fan hub that uses an external power source (like a SATA power cable, which can provide 54 Watts of power). This way, you no longer have to worry about an amperage budget.
Good to know: if your PC fans seem too loud, you may want to perform some basic repairs.
A Word on AIO Water Coolers
Even as computers have become much easier to assemble than in the quagmire years of the 90s, the lack of standardization of water coolers is still somewhat present. The process is still pretty straightforward, as long as you stick to the instructions on your system.
AIO water coolers are meant to be the easiest to install, but may sometimes give you some vague instructions on where to connect the 4-pin header. A header meant to control the fans should always be connected to the CPU FAN.
In most cases where there are two 4-pin headers, one would be meant for the fans, and the other would power the pump. Ensure that the fan header is connected to the CPU FAN and the pump header goes to the AIO PUMP port of your motherboard. If your motherboard doesn’t have one, check the manufacturer’s instructions to see whether it’s possible to put it in CPU OPT.
To avoid confusion, most AIO coolers will require a SATA power connection from your power supply and an additional USB header to control certain features via software (e.g., LED colors, pulse-width modulation, and effects).
Read your manufacturer’s instructions very carefully to avoid operating your system with an improper cooler connection.
Going a Little Further
If you haven’t yet purchased a cooler for your CPU and are still pondering on what to put in your CPU FAN and CPU OPT ports, have a look at our guide on what equipment you should get, and weigh the pros and cons yourself!
Don’t forget that the cooling setup isn’t the only thing that your CPU’s performance lives and dies on. You should also look into what kind of voltage regulators your motherboard has. A new motherboard could actually give your CPU a splash of life if it’s not performing as it should.
Image credit: Pexels
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