Fan Connections for Cooler Master K280 vs Gigabyte GA-990FXA-UD3 R5

Question

I'm mounting my first computer and I'm confused about how to connect the case's front fan to the motherboard. This is what I have:

• Case: Cooler Master K280
• Motherboard: Gigabyte GA-990FXA-UD3 R5
• CPU: AMD FX-8320 8-core
• Heatsink: Cooler Master T4 Hyper
• Extra fan: second fan at the back of the case for exhaust

^{fan connectors are circled and identified  (Click image to enlarge)}

Both PWR_FAN and SYS_FAN2 are 3-pin connectors. SYS_FAN1 is a 4-pin connector.

I've installed a second fan at the back of the case for exhaust and the only connector in range (the only one that can be reached with the original cable of the fan) was the PWR_FAN.

The front fan can only reach SYS_FAN1, which is a 4-pin connector (the front fan is a 3 pin connector.

My question is, in this case, what should I do? I see 4 options:

1. Connect it to SYS_FAN1 anyway, leaving one pin "unused". Can I do this? Which pin should I leave unused?

2. Get an extension cable to connect it to SYS_FAN2. I don't even know if such a cable exists.

3. Connect it directly to the power supply using the adapter that comes with the case.

4. What I'm doing is all wrong and I should connect the fans some other way. Please advise.

Answer 1

You can connect a 3 pin fan connector to the 4 pin header (It should have a plastic clip that only allows it to fit over the correct 3 pins). The 4th pin is usually used for speed control, not an essential feature, it means your fan will either be on at full speed, or off.

The most important fan to have connected correct is CPU_FAN which it sounds like you have, as this will usually scale up based on the temperature detected at the CPU. Without this one, your CPU could get extremely hot and it might be ramping up an intake air fan instead, which wouldn't be too useful. But as I said, I think you've covered this.

SYS_FAN2 and PWR_FAN are likely the same, as they're both 3 pin. As such, PWR_FAN is probably labelled as such because it's in the most convenient place, traditionally, for a power supply fan. Using this is fine.

As for your options:

Option 1. Yes - Do this one.

Option 2. These do exist, but you don't need it in this situation

Option 3. Also an option, but not necessary in this instance

Your motherboard manual (located here) has further information:

3/4/5) CPU_FAN/SYS_FAN1/SYS_FAN2/PWR_FAN (Fan Headers)
The motherboard has a 4-pin CPU fan header (CPU_FAN), a 4-pin (SYS_FAN1) and a 3-pin (SYS_FAN2) system fan headers, and a 3-pin power fan header (PWR_FAN). Most fan headers possess a foolproof insertion design.

When connecting a fan cable, be sure to connect it in the correct orientation (the black connector wire is the ground wire). The motherboard supports CPU fan speed control, which requires the use of a CPU fan with fan speed control design. For optimum heat dissipation, it is recommended that a system fan be installed inside the chassis.