CPU Scaling and Performance
Increasing the Core i7's operating frequency 90% from 2.0GHz to 3.8GHz only yielding a 9% performance boost, so Core i5 and i7 users will gain very little out of overclocking.
Despite packing a more efficient architecture and higher operating frequencies, the 2500K and 2600K processors were slower than the 920 and 750 processors. In fact, the Sandy Bridge-based parts were also slower than the Phenom II X4 980 and X6 1100T.
It was also interesting to see that Dirt 3 really dislikes dual-core processors as the Phenom II X2 560 averaged 54fps, making it effectively twice as slow as the Phenom II X4 980. Another fun fact: Dirt 3 seems to prefer hexa-core processors over their quad-core counterparts as the higher clocked Phenom II X4 980 performed worse than the Phenom II X6 1100T.
The Athlon II processors also has a pretty weak showing compared to the Phenom II and Core range, delivering roughly half the performance regardless of their core count. This would suggest that the L3 cache of the Phenom II processors is quite important here.