I have a fairly powerful computer. I can play Shogun 2 fine with everything maxed. I can play Napoleon, Empire, with everything maxed and no problem. I can play Skyrim with everything maxed and still get a decent 30-40 FPS. But Rome Total War lags on the battlefield in large battles! Especially with RTR but even in vanilla. The mouse response is sluggish and also has a strange inertial effect making it very difficult to select units or do anything. The camera is also sluggish. Can anything be done to improve performance? (Except the obvious: reduce unit size to small, reduce graphics quality to medium, etc. I don't want to do that).

Someone suggested that RTW is only using one core of the CPU. Is it possible to make it use more cores?