BallistiX DDR500 or XMS Pro 4000

I got Corsair XMS PRO 4000 (3-4-4-4-8 ) , I can't get it past 255FSB with P5P800 Board due to the 865PE chipset. It runs higher with 875P chipset though. Currently, I only ran 245FSB without any problem. I had a chance to swap my RAM with 1G Crucial BallistiX DDR500 ( 2.5-4-4-8 ), I saw some review, it won't go much higher with 865PE chipset as well. Is it true ? How high can anyone got with those crucial?

Thanks