CiM uses both of my cores, or at least I got load on both in my quick test with task manager.
0.14 Ghz CPU difference wouldn't be this catastrophic (E6300 is 1.86 Ghz per core) ... also the 8800GT OC is a beast, which can easily handle this game as far as I know...
once again doesn't explain why other, much more graphic intensive games are working fine then ?
Shortish, basic, explanation to be taken with grain of salt: CPU and graphics PU do different things. Basically, a cpu tells a gpu what it needs to draw and where, while the gpu does the computing necessary for the practicalities of drawing, ie rendering the polygons/ triangles, filling, texturing and making sure the results go to video. But while there is the potential to use a gpu for 'helping' a slow cpu (eg physX, CUDA) they either aren't generally used in games or are irrelevant here. In CiM a good cpu is clearly important and the most likely reason is because you have a lot of entities, simulated people, all wanting to do pathfinding to do their desired trips quite apart from any goal and mood analysis going on. Pathfinding is a renowned cpu killer even in games with only a few entities simulated, if there are potentially thousands it will put a huge drain on the cpu and there really isn't a way to avoid that.
That is why you get the (vsync limited, presumably) 30 fps at pause- when paused none of the entity simulation is running so the cpu can supply the gpu with information easily. As soon as the simulation starts running the cpu bottlenecks and cannot supply the gpu with the information it needs- the gpu cannot draw without knowing where the stuff is- resulting in the fps drop. The reason why CiV runs fine is because its cpu load comes mainly at turn endings. If you have played civ4, or especially civ3 you'd have noticed that towards the end of games hitting the end turn button can result in a considerable amount of pause before it's your turn again, which is the cpu doing all the necessary calculations for the AIs' turns. A better gpu will not speed that up either.
I have an e6400 so to an extent I share the pain. My fps are about 50% higher than yours. But overall you'd get far more mileage from overclocking the cpu than the gpu for CiM.
