CPU Performance
Going from just 2.5GHz up to 4.50GHz, which is an 80% increase in frequency, only resulted in a 14% increase in performance when using the Radeon HD 7970 GHz Edition graphics card at 1920x1200. Therefore, while there is some performance to be gained overclocking a Core i7 processor it isn't an effective way of boosting Black Ops II performance.
When going from 2.5GHz to 4.5GHz with the AMD FX-8350 we only saw a 12% increase in performance, going from 94fps to 105fps. Given the default frequency for this particular processor is 4GHz there is not a great deal of headroom here.
Call of Duty Black Ops II is optimized for dual-core processors and we saw constant activity across four threads in the portion of the game that we tested. Most processors allowed the Radeon HD 7970 GHz Edition to render between 97 and 104fps, which is only a 7% difference. The only processors to really drop below 97fps were the Phenom II X6/X4/X2 and Athlon II X4/X2.