I just built this system with Asrock z77 Extreme 4 mobo and ivy bridge core i5 3570k ( applied Arctic silver 5 instead of the factory thermal paste). When I power the system on, the cpu fan (stock) does not start until a few seconds later - and stops almost immediately. Then again 2-3 seconds later it starts to spin normally. I tried powering on with the on board power switch with the same result. Any guess what the problem may be? Thanks a lot in advance!
I just chatted with Intel Customer support - they say it is normal for the brand of the stock fan - NIDEC. At startup, the controller tries to detect the rotor position, adjusts itself, then starts at full speed.