haha, I was thinking about a wall or a combination of BIOS settings(damn too much bios settings for this board ), cause it's 100 % stable at this freq, end when I add only 1 more mhz, I have an instant blue screen.
So I tried higher voltages(as Karl said, these are high), and still cannot get 521 Mhz.
Hum I have to try the 2 other 6320 I have to find if they have this same wall too.
Thank you guys for the confirmation.