CPU Fan speedig up for no reason!

[SgtMykee]

Hi guys!
Sorry if this kind of thread is already exist but I didn't found it yet!

So my problem, I''ve just bought a new ASUS Z97 Sabertooth Mark 2 motherboard, with Intel I7 4771 processor!
Everything is working fine, the intel ventilator is working perfectly, my cpu didn't went upper then 50 degrees celsius while gaming.
But for no reason sometimes the fan on the CPU is speeding up to full speed for 2 max. 3 seconds but the heat is only 40-45 celsius during gaming.

Normal CPU temperature is 30-40 celsius, fan speed is 900-1100 rpm max. monitored with ASUS AI Suite 3.

I planned to buy next month Corsair H110 water cooling on my CPU to get the best cooling, but those speeding up things freaks me out!

I have the latest BIOS and Windows 8.1 update aswell.

p.s: sorry for my English but I think its clear what I say

 

[Robert17]

Your thermal sensor for the CPU is reporting an up-tick in core temps on at least one of the cores. When that happens your MB sends a signal to increase the fan speed via the MB fan header. The spike in temps may be minimal but enough to trigger the software to react. If the fan speed settles down after a couple of seconds the MB is doing it's job. Nothing to worry about.

 

[doyll]

Sounds like your CPU fan is operating on variable voltage. Voltage control usually gives 3 speed levels. PWM control give almost infinite speed levels.

Couple of questions:
Is the CPU fan PWM or variable voltage?
If fan is PWM, is bios set to PWM fan control?