For the people who own these boards, how how are you able to take the FSB?

I was able to do 500MHZ FSB 1:1 with 4X1GB perfectly fine. Which is something neither of my P5B-Ds were able to do. I tried finding the Max FSB last night but couldn't pull more than 520MHz without it locking up within a few seconds of Orthos. Although I tried with 4 sticks of ram.

So people with this board, could you take it much higher than 500MHz FSB?