Sounds like you may have hit the max for your cards core. It seems strange why I can get another 100mhz on the core than you can. I suppose each card is different. I had an interesting run of 3dmark05 last night. My previous score with my old 4000+ clocked at 2.6ghz card at 640/1270 scored 7620. My new cpu a X2 3800+ clocked at 2.2ghz and the card bumped slightly to 650/1270 scored 7626. I'm liking this new cpu lol!