@ Panging & SpeedEuphoria ,I try to play a lot with Cpu Reference and had no success with stable in 550 x 8 I try around 0.745-0.9 this range I can hold PC stay no blue screen. Also I try to adjust MCH/DRAM reference no success . I'm sure Cpu Vcore is enough for me to hold 4.40 (550x8) and my new ram kit can do 550 with 5-5-5-15 and not loosen subtiming very stable.

Any one try to play around with Cpu clk skew and Mch Clk skew ?
Now I 'm using MCH skew around 150-200 PS and seem nothing change...