One fan header is too slow

[Warpspasm]

My one motherboard fan header has a 4 pin interface. There is a guide that shows you where to plug in a 3 pin fan cable, which I did. But, the fan that plugs in there operates at about half speed of the other fans. Even the LED is dimmer. What's up with that? The header says sys_fan2.

 

[akhilles]

What fan is it? 4-pin is for cpu fan. If it's slow, disable fan control in bios & set it to manual at 100%.

 

[Warpspasm]

I'll try that. There is already a header for the CPU fan. I guess this is just an additional PWM fan header.