Gigabyte CPU_OPT Fan Not Always Spinning

[Evil Closet Monkey]

I have a GA-Z87X-UD5 TH motherboard with a Corsair CPU fan and radiator, with the 4-pin radiator fan plugged into the CPU_OPT plug.

Most times when I power up the computer from OFF the fan will not spin. Running Prime95 gets my temp well over 80C with no motion from the fan. If I plug one of my 3-pin case fans into the plug it immediately spins up.

Rebooting the computer causes the fan to spin right up and keep running!

The other night I did a reboot and started & stopped Prime95 multiple times. Each time the fan started when it needed to, and stopped when it cooled things down. This evening the fan appears to want to keep spinning after the reboot, despite the CPU temp being down to 20C, or less.

Am I dealing with a bad temp sensor somewhere, or perhaps I did something that is causing confusion with the fan? How can I make sure my CPU_OPT fan will spin when needed?

 

[Karadjgne]

I would not plug cpu fan into cpu-opt. I would plug cpu fan into cpu_fan and find a different source of power for the pump, if it's 3-pin it'll work in cpu_opt. In bios look for your fan duty cycles. Set cpu fan for standard or performance mode and if your bios allows, set cpu_opt as disabled or 100%.

The cpu fan should always be spinning, no matter what, but due to temps, it'll spin slower at cooler temps and faster when the cpu gets warm.

If push comes to shove you can set all duty cycles to standard or performance except cpu_opt and use speedfan.exe to control all other fans after Windows is running.

 

[Evil Closet Monkey]

The CPU fan (3-pin) is plugged into CPU_FAN, with the radiator fan (4-pin) plugged into the CPU_OPT port.

I will look at setting CPU_OPT to always be at max speed. However, should it not spin up and down with the CPU temp rising and falling?

Thank you!

 

[Karadjgne]

What exactly do you mean by cpu fan is plugged into 1 port and radiator fan is plugged into another? The cpu fan should be the one cooling the heatsink/radiator from the cpu, not 2 different fans. The only other fans should be the case intake and case exhaust.

Unless you purposely decide to set a fan to 0% duty cycle, all fans should spin at all times, usually in the 600-1200 rpm range, although that can vary with the fan.

 

[Evil Closet Monkey]

I have a Corsair Hydro Series cooler, which has two fans. CPU_FAN powers the fan that sits on the CPU. CPU_OPT is powering the fan that cools the attached radiator - which sits on the rear case fan.

http://www.corsair.com/en-us/hydro-series-h60-high-performance-liquid-cpu-cooler

The fan plugged into CPU_OPT is definitely not spinning all the time. It seems that the CPU temp must be over a threshold when the PC starts up for it to kick in at all.

I can set it to spin at max speed all the time, but it should be able to speed up and slow down to limit power and noise. At least that is how I understand it with a 4-pin. Am I misunderstanding?

Thanks for the help!

 

[Karadjgne]

Ok, follow the link you posted and take a good look at that picture. The square block that says "corsair" is not a fan, its a pump and must run 100% at all times, this is extremely important.

Now, some motherboards will give you control of cpu_opt with 3-pin fans, some will not. Corsair directions will state to plug the pump (3-pin) into cpu_fan header, and power the fan on the radiator some other way. Motherboards have a failsafe alarm which will shut the pc down if they do not detect a spinning fan on cpu_fan so that's why the directions are that way.
I personally prefer it the other way. Since cpu_opt is not controlable for me, it gives 100% power at all times on 3-pin, so thats where I put the pump. I put the 4-pin fan attached to the radiator on cpu_fan so it has control. In bios set your fan speeds to either 'standard/normal' or performance mode. Make sure it looks just like the picture, the air from the fan should be blowing out the back of the pc.

So.

Cpu_fan = fan on radiator = performance/standard

Cpu_opt = pump on cpu = disabled/100%

This is why your temps spike, you have the pump varying speeds instead of running 100% and the fan cannot cool water that isn't moving through the radiator.

 

[Evil Closet Monkey]

I'm not sure where I grabbed the instructions to plug the pump into the CPU_FAN and the radiator fan into the CPU_OPT. A combination of vague instructions and this being the first time I installed a pump system being at least contributors.

I swapped the power points and updated the BIOS to have CPU_OPT run at 100% at all times, with CPU_FAN set to "Normal". It certainly made a difference! Idle temp dropped several degrees C. A 90-minute Prime95 averaged around 45-50C. Definitely a much better situation!

Appreciate the help and the education!

 

[Karadjgne]

No worries, its what we are here for, and yes, while a very good cooler, the directions are somewhat lacking in new user friendliness. 😉