I ran into the same problem. I started a game on the huge map with all possible civs. In the beginning, the time between turns was about 1 sec. I was playing a cultural/science development game. When I got to steam power, turns took about 2 minutes each. I have a 1.4 ghz Athlon, and I had animations turned off, so I assumed it was my 128mb RAM. But I increased RAM to 640 mb and the improvement was minor if any, so I don't think that will help most people. I checked the system monitor (Windows ME) and found that I was using 100% CPU most of the time, nothing else seemed stressed. Then I started up in diag mode with nothing else running, to get rid of background stuff, but that didn't make a difference either. So I am assuming that huge map with lots of developed competitive CIVs just takes a lot of time - say an n-squared problem. Personally, I am willing to put up with the 2 minute wait to play the big game, but I miss the instant responses of the small games and Civ II (perhaps the Mac version will be better - it was for Civ I and II).