Question My sffpc has 1 sys_fan header and 1 cpu_opt, which setup for an intake & exhaust fan should I use?

Coyle · Mar 14, 2025

Should I put them both on the sys-fan header with a splitter or can I attach one of them to the cpu_opt, and if so which would be best to go there, the 200mm intake fan or the 80mm exhaust fan? Thanks!

Edit: I see my motherboard has Smart Fan 6 which allows CPU_OPT header to be switched from the default CPU setting to System 1, which is also the setting of SYS_FAN. Curve profiles can also be adjusted if needed, though has a TUNE ALL feature as well.
So does that mean I'm ok to use CPU_OPT header for one of my fans, and if so does it matter which one? Or, do I still need to put the both on SYS_FAN with a splitter?

This is my first gaming build and don't have any experience with cooling systems.

Brainonska511 · Mar 14, 2025

You should be fine using the extra CPU fan header as a system fan header, especially if you can change settings for it in BIOS. It's probably originally there for people using AIOs that need the extra header for the pump.

Nothing wrong with using a splitter either, but if the fans are different sizes or types (eg, 3-pin and 4-pin), you might see some weird things with fan speeds.

mindless1 · Mar 15, 2025

Yeah, one fan per header gives the best individual speed control for different types/speed-range/etc fans, except you're stating that if you switch it away from CPU, they both share the same setting? If so, I'd try it and see, but the best match of speeds might be achieved some other way. 200mm front fan doesn't need nearly as much RPM to move air compared to the 80mm, yet is more audible at same RPM (all else equal except it being in the front, potential line of sight path to your ears?). If any are 4 pin, plug into a 4 pin header if available.

Brainonska511 · Mar 15, 2025

Considering that case, you might be able to get away without the exhaust fan at all, especially with such a large intake. 80mm fans don't move a lot of air.

Paperdoc · Mar 16, 2025

I advise you keep the small exhaust fan in use. The case does need exhaust.

Do NOT worry about making fan SPEEDS match. Obviously with two fans so different in size, the AIR FLOW each generates will be very different at the same speeds, and it is that FLOW that matters. With such mismatched sizes the air flows will never be equal anyway.

FYI, the signal sent out by any fan header is NOT a speed setting. It really is a "% of full speed" setting, so the actual speed of each fan for the SAME signal is different.

If you are using the two headers, one for each fan, I suggest you set the "fan curve" of both headers the same.

Question My sffpc has 1 sys_fan header and 1 cpu_opt, which setup for an intake & exhaust fan should I use?

Coyle

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Brainonska511

Lifer

mindless1

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Brainonska511

Lifer

Paperdoc

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