Bungie redid the Halo engine for PC in a downloadable multiplayer add-on, there is a 60% increase in the performance for all hardware that supports pixel shaders. I would assume that the same engine, or a very similar one is being used for Halo 2 Xbox [ with alot of new stuff in the engine of course ] so we can expect either more FPS or more graphics in Halo 2 , or both.