Improve battle performance?

Heya

During bigger battles (5000+) I met some lag - unit animation ar so so, not freezing, but when i move camera through the battle field, it starting to jerk on every 10 yards, thats anoying..but the question is:

I started to play on highest settings with huge units, glints and other beauties - after some time I decreased all, then decreased everyting a little bit more, than decreased almost to Zero (from 4x anti to trilinear, medium textures ant so on). But nothing changed. Unit's animation in big battles - so so, camera stops for a 0,002 sec on every ten yards when moved through. so what has biggest influence on battle performance? I drasticaly changed all settings, but cant see any difference in performance....I played ETW with 12 000 units on battlefield, NT with the same - and lag was very very little. and now THIS dream game with unespected issues

By the way, should I turn on FPS booster in cow folder, or it starts automaticaly, when I starting the game?

And one more question - could it be, that one faction is lagging at little bit more than another? due to armor detailes and other things?

It's not the graphics settings if you have a reasonably up-to-date graphics card. The problem is the game engine only using a single core, even if you have a quad core. Best processors for medieval 2 are 3.0ghz +, doesn't matter how many cores.