First of, thank you Eva, i bet i will use your tips and guides in near future...
Second,... I just finished my DFI x58 UT + 920 D0 build yesterday, poped the bclk @ 166, HT&Turbo ON, installed OS and all the other stuff... Later i started to play with the clocks, i have noticed some weird noises from the PWM area. When SYSTEM temp. hits around 58-59° under small FFT's prime, the board starts to sing - whistle. This stops immediately when i stop the torture test. My question is, is this safe? What are safe 24/7 temperatures for the PWM and NB?