Benchmarks: CPU Performance
The only processors to really drop off in terms of performance were the AMD FX-4320, 6350, 8320E and Athlon X4 860K. The Pentium G3258 and G4400 both sustained over 90fps, while the Core i3 processors were good for 100fps+.
For those with extreme GPU setups trying to achieve the highest frame rate possible, it will pay to overclock that Core i7 processor as high as possible as there will be more performance to be had. However, those running a single GeForce GTX 980/970 or anything slower for example, probably won't gain much through overclocking.
It seems no matter how hard you push the AMD FX-series (within reason) it isn't possible to match the out of the box performance of the Core i7-6700K and likely previous generation models as well. Still those with an FX processor are most definitely going to want to overclock the snot out of it.
The pesky little Pentium G3258 makes out like a champ in Doom, delivering 8-core FX-like performance and better at the lower clock speeds. So there you have it, (single player) Doom runs perfectly well on a dual-core Pentium processor.