TL;DR: Old CPUs suck, have at least 4 threads, buy a modern Intel CPU and overclock it, look up Cinebench R15 single threaded benchmarks.
Disclaimer: I do not have a master degree in CPU engineering, software engineering etc.
Over the years, Vindictus has steadily gotten more demanding as more effects get added, resulting in crippling performance on older computers, even on minimum settings. The game indeed ran perfectly fine on older hardware such as Core 2 Duos, but that was when Season 1/2 was the latest content. Unfortunately, for gamers with older computers, Vindictus is an evolving game and as it ages, it demands more resources. Somehow, this has lead to the belief that GHz means everything and the fewer the threads the CPU has, the better the game runs. This might have evolved from the generally agreed theory that the game is heavily single-threaded dependent.
Another theory I hear get thrown around is AMD sucks, even Ryzen. Yes, they do suck at getting 500 FPS in CS:GO, but for the most part they are plenty good.
But no worries, because today is the day we hopefully clear everything up!
Note: Only relative performance should be considered.
We will focus on five CPUs: E7500, Q6600, i7 2600, i7 2600 (1C/2T) and i5 6600.
Compared to the Q6600, the E7500 has faster single threaded performance, but due to half as many cores, it has relatively low multithreaded performance. We can gauge their rough performance with Cinebench R15 (free download if you want to compare your CPU).
So theoretically, if Vindictus is purely single threaded the E7500 should be significantly faster, however, it turns out the Q6600 actually pushes more FPS than the E7500 95% of the time. We can also see the E7500 is mostly maxed, almost always hovering around the 95% usage range while the Q6600 hovers around 60%. This enforces the theory of Vindictus utilising more than one thread.
7 FPS vs 10 FPS
Yes, performance is terrible on both CPUs, but we are testing relative performance.
Anyway, if the game indeed uses more than 2 threads, why is the i7 2600 (1C/2T) so much better than the quad-threaded Q6600? After all, the Cinebench R15 score of this CPU is only 133/170 compared to the Q6600's 64/244. A possible theory is the main game engine can only run on one thread, but other parts of the game can run on a separate thread. Let's use the audio engine as an example. In the case of the Q6600, the main game gets bottlenecked on its low performance core, while the audio engine can spill over to the other cores. In the case of the i7 2600, its significantly faster core can tackle the main game engine better and the less demanding audio engine spills over to the second hyper-threaded core. Now that the main game engine can run at full speed, overall FPS increases.
As we can see, the idea of Vindictus utilizing more than one thread is enforced by the comparison of the i7 2600 (1C/2T) and the full fat i7 2600.
24 FPS vs 38 FPS
The i5 6600 is the clear winner out of all the CPUs. Multithreading performance is equal to the i7 2600, but it screams ahead in the Cinebench R15 single threaded benchmark and real world Vindictus performance.
38 FPS vs 50 FPS
From the testing, it is fairly conclusive Vindictus values single threaded performance the most, but that does not mean a single threaded or even dual threaded CPU is enough to not take a performance hit assuming unlimited GPU performance and RAM bandwidth. The hard thread limit is probably around 4 but until it has been confirmed, we can only guess. For posterity, look up Cinebench R15 benchmarks or any single threaded benchmark as they seem to offer a good indication of Vindictus performance. Please note RAM bandwidth can influence benchmark scores, and it is unknown how important RAM bandwidth is for Vindictus.
Full benchmark video:
TL;DR: Old CPUs suck, have at least 4 threads, buy a modern Intel CPU and overclock it, look up Cinebench R15 single threaded benchmarks.