I'm able to run the 5ns ram on my Palit Daytona GF3 Ti200 at 530Mhz too, never imagined 5ns ram ot do that well. And the heatsinks aren't applied well, doens't cover the ram modules fully (2mm on each side of the ram modules aren't covered by the heatsink and they're applied with some tape.
It woun't go faster than 530 though, xarar, consider yourself lucky. According to what I've read even 4.5ns doesn't necessarily do that well.