Radeon 9500 Unlocked question

[[Food] Food-Giant]

So, I have had my Radeon 9500 unlocked for quite some time now. I get some checkerboarding (mostly menus for some reason) but all games are still very playable. I played Steam's newest map for CS, de_nuke with HDR enabled. Interestly enough, the HDR takes away the checkerboarding... my question is why? I notice a drop in framerate with this map, which is why I am wondering. Does the HDR somehow cancel out the unlockedness of my video card? Help me I'm clueless.