No idea what my motherboard does with my fans

[Powerpuncher]

Hey,

so I've been undervolting my CPU on the weekend and it seems to be stable at 1V. But I ecountered a problem with my main CPU fan in the process of undervolting. It randomly ramps up to 100% and satys at 100% for a random amount of time and then ramps down again to around 800 rpm. I didn't change anything in the BIOS other than the CPU VCore. The temps are low and there is no reason at all for the fan to ramp up.

I tried loading the default profile for the BIOS, but it didn't help and now I'm kind of clueless. Did I somehow manage to corrupt my BIOS?

Intel i5-4670
Gigabyte Z87-D3HP
G.Skill Ares 8GB DDR3-1866
Gigabyte GeForce GTX 770 WindForce 3X OC
Cooler Master G600 600W

Already searched on google quite a bit, but couldn't find anything.

Regards,
Pp

 

[dalewakelin]

Thats what is supposed to happen default, try going into fan profiles in bios there could be a fix in there. If it bothers you that much you could get a fan speed reducer and run it off a fan controller.

 

[Powerpuncher]

I'm pretty sure ramping up the fan to 100% keeping it there for a random amount of time (sometimes for hours) and then suddenly going all the way back down without any reason is not supposed to happen. If the CPU would've been hot, I would understand it, but the CPU basically runs at room temperature...
And I already tried changing stuff in the BIOS that is in some way related to the fans...

Edit: Some BIOS settings:

Edit: It just ramped down to 700 RPM after 5 hours of constant 1800 RPM. From 1800 to 700 for no apparent reason...

Edit: Ok, I've tried updating the BIOS. The BIOS looks a lot better now, but it didn't fix the problem. But what seems to have fixed the problem is simply switching the OPT_CPU fan with the main CPU fan. No Idea what's that all about, but if it keeps working I'm happy.