How to Reduce Assassin’s Creed IV Black Flag Stuttering

Let me put this first: this guide provides no ultimate and definitive solution. It will heavily reduce stuttering, but it won’t be able to get rid of the stuttering entirely.

Two methods

Now that we finally have a mod to play this game with more than 60 FPS (just took us 10 years) this might become relevant for some people. The game was clearly designed and optimized for 60 FPS. The frametime graph is basically a fixed and steady line at 60 FPS.
Anything above that, even just 80 FPS and stability goes out the window. It’s just hitching all the time. Not as bad as in some recent Unreal Engine 4 titles, but still annoying.

As it turns out the game doesn’t like Hyper-Threading, or Simultaneous Multi-threading as it is also called. Using RTSS to display the core usage shows that one CPU core is utilized heavily while all others are not utilized very much and are quite jumpy. There is two completely different methods to “fix” this and both have something to do with core affinity.

1: Download Process Lasso and install it. Boot up the game, head into Process Lasso and right click the AC4 process “AC4BFSP.exe”. Head for the setting called “Core Affinity” and disable either Hyper-Threading or SMT. The name depends on your brand of CPU. This will force the game to just use your actual physical cores. Minimize Process Lasso and go back to the game. It runs a whole lot smoother now. Not perfect, but a huge improvement.

2: If you don’t wanna use external tools just follow this helpful video:

As you can see you can use Task Manager in a very similar way to Process Lasso, albeit with some extra steps. This fix doesn’t change anything about AC4’s inherent problems with Hyper-Threaded virtual cores, but it also fixes the problem of AC4 just using one core extensively while not utilizing the other ones properly. Ignore the other fixes in the video. The FPS cap is entirely up to you and the triple buffering thing he shows doesn’t do anything. In any case this is just as effective as Process Lasso.

I don’t know in detail in what exact way these two methods differ, but they both worked for me in equal measures. In any case AC4 is not very good at fully utilizing the potential of modern CPUs and the provided fixes are ultimately just glorified band-aid. Maybe someone talented will come up with a true fix. Ubisoft does not care about making their games future-proof, such as Valve does with nearly all of their titles. Just look at how bad Far Cry 3 or 4 run on even the most modern gaming rigs.

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