system starts to run slow later in game

Hi

I have a 3.0g P4 with 512 ddr, running windows xp, and the problem I keep running into is late in the game the game takes forever to go between turns. I have tryed running the game on several differnt computers with the same results. I have used all the patchs given out my civilization officially. Is there anyway to speed up the game???

Thanks

Are you running Large/Huge maps? Are you running with a lot of AI civs? Does the AI have a lot of cities, and/or a lot of units? Does the AI have railroads?

The more "yes" answers, the slower the game will run.