As a first person shooter we were not expecting to see much in the way of CPU utilization on Metro: Last Light, but we were wrong. We were pleased to see AMD FX-8350 and FX-6350 processors performing really well at ~ 65fps. Expecting the FX-4320 to deliver somewhat similar performance, we were shocked that frame rates dropped ~15% when going from 6 threads to 4 threads.
After that result it was hardly surprising that the AMD dual-core processors were slaughtered and even the Phenom II X2 570 managed just 28fps when coupled with a GTX Titan. The Core i3-3220 got off lightly thanks to its HyperThreading support which enables 4 threads.
As usual, Intel Core i5 and Core i7 processors reside at the top of our chart allowing between 68 and 72fps to be rendered.
Underclocking the AMD FX-8350 to just 2.5GHz didnt have a huge impact on performance, it seems as long as you have enough threads available Metro will play very well. We saw a small 13% reduction in performance when dropping the clock speed by 44%.
Running a similar test with the Core i7-3770K processor it was much the same, dropping just 16% performance from a 44% reduction in clock speed. It's worth pointing out that the 3770K clocked at just 2.5GHz produced the same performance as the FX-8350 at 4.5GHz.