SYS_FAN2 slower than SYS_FAN1 and PWR_FAN?

[Mark]

I have two identical fans, and I've swapped them around a bit.

[ Modify: This is the GA-P55A-UD6 ]

SYS_FAN1 runs at about 1300RPM
SYS_FAN2 runs at about 690RPM
SYS_FAN3 runs at about 1300RPM

CPU_FAN runs at about 1300RPM
SPU Smart FAN Control is disabled.

I notice that SYS_FAN2 and CPU_FAN are the four-pin headers, and SYS_FAN1, SYS_FAN3, and PWR_FAN are all three-pin headers.

Is there any reason why SYS_FAN2 runs more slowly?  Can it be controlled in any way?

Thank you.
Mark

[Beekeeper]

 
strange

try with new bios.
use different vendor fan just to try what will happen

i don't think SYS_FAN2 can be controlled, but you need to check in manual and in bios setup in HW monitoring options after enabling Smart FAN. also worth to check under Easy Tune 6 software as it has some options for fan controll but i am not sure if it's able to control this particular fan