In my opinion, the HD6850 should be fine for higher IRs, but this may depend on the game. Which game did you try to run? Some of them are quite hard because of EFB copy to RAM, or BBox, or EFB access, or real XFB, ...
Edit: I've seen you're mention mario kart. So Wii or GC version? Do you have anti-aliasing enabled? Especially SSAA is really hard. Maybe also try to set "ignore format changes" in GPU hacks while the game is running.
Edit: I've seen you're mention mario kart. So Wii or GC version? Do you have anti-aliasing enabled? Especially SSAA is really hard. Maybe also try to set "ignore format changes" in GPU hacks while the game is running.
