General CPU Performance
Seeing how drastically Civilization V scales when using a Core i7 processor at various frequencies, let's look at different processors and platforms. The Core i7 920 and Core i5 750 delivered the exact same performance at 1920x1200, meaning that the i7's extra memory bandwidth, memory capacity and Hyper-Threading support offer no benefit when playing Civilization V, and this is often the case with computer games.
The AMD Phenom II X4 970 performed reasonably well, but despite its higher clock frequency, it was 13% slower than the Core i5 750. Surprisingly, the Core i3 540 (dual-core with Hyper-Threading) was 9% slower than the Phenom II X4 970. Even more shocking, the Core i3 540 was faster than AMD's mighty Phenom II X6 1075T (hexa-core).
The Phenom II X4 970 is clocked roughly 17% higher than the Phenom II X6 1075T and it was 14% faster even though the Phenom II X6 1075T has two more cores. Civilization V doesn't use six cores, but that's to be expected. It appears the game can use up to four cores, but not aggressively so.
The Core i3's Hyper-Threading is enough to give it a real advantage over standard dual-core processors and the efficiency of its architecture makes it more powerful than the Phenom II X6 in this game.
The Pentium G6950 was 17% slower than the Core i3 540, but that's to be expected with less cache and no HT. The Core 2 Duo E8500 was on par with the G6950. We found it interesting that the dual-core Athlon II X2 260 was 2fps faster than the quad-core Athlon II X4 645, thanks to its slight clock speed advantage. Finally, the old 2.40GHz Core 2 Quad Q6600 was the slowest processor tested, delivering just 20fps.