The above CPU results have been arranged by the minimum frame rate result rather than the average. Rise of the Tomb Raider is surprisingly demanding on the CPU and while not as extreme as some of the games we have tested in recent times it still requires a decent processor to get the most out of a high-end GPU.
There is a noticeable performance jump from the Core i7-4770K to the new 6700K. Rarely in games do we see a margin like this but keep in mind the 6700K is clocked 14% higher. When comparing minimum framerates, the 6700K was 17% faster.
Looking to AMD's processors, we find the FX-series producing some rather impressive average frame rates. Even the minimum frame rates aren't that low, though we do see that the FX-8350 is comparable to the Core i3-6100.
Once we get down to the dual-core Pentium G4400 performance really starts to drop away and surprisingly it is the Athlon X4 860K that provides our lowest minimum frame rate result.
Initially I had attributed the rather large performance gap between the Core i7-4770K and the 6700K to the fact that the 6700K was clocked 500MHz faster -- that and the updated CPU architecture. However, once we underclocked the 6700K all the way down to 2.5GHz, the frame rate performance when paired with the GTX 980 Ti goes unchanged.
Although we have seen this kind of thing in other games the scaling performance almost always goes unchanged when the general CPU performance is the same. The results seem unlikely but having re-tested multiple times we haven't seen a drop in performance with the 6700K, with more time I plan to run some scaling tests using the Haswell Core i7 as well.
The average frame rate performance of the AMD FX-9590 isn't greatly different when comparing the 2.5GHz and 4.5GHz results as the higher clock speed is just 14% faster. That's an insignificant margin for an 80% increase in clock speed but if we look at the minimum frame rate we find that the FX-9590 became 35% faster when going from 2.5GHz to 4.5GHz.
Finally let's look at how the fan favorite dual-core Pentium G3258 Anniversary Edition processor scales. This chip comes clocked at just 3.2GHz by default but overclocking it to 4.5GHz offers a substantial boost in average frame rate performance. Oddly the minimum frame rate almost maxes out at just 3.5GHz where it dipped to 44fps. The dual-core processor seems to be creating some kind of choke point that boosting the frequency can't overcome.
Still with a minimum of 47fps and an average of 77fps the Pentium G3258 still enables playable performance.