Games utilize CPUs and GPUs differently, depending on a variety of factors, and pretty much everyone agrees you need not just a strong GPU but also a capable CPU for modern games. However, you must have wondered why, despite multi-core CPUs being a thing for over two decades now, games still aren't able to utilize them to the full extent one may expect.

Your graphics card might be bending over backward trying to squeeze out every last frame out of the game, running at near-100% utilization, but your CPU will be over there chilling in the corner, barely breaking a sweat. If this curious behavior of modern 6-core and 8-core CPUs (or basically any other processor) has puzzled you, here's a brief explainer about why this is the case.

Making games utilize more cores is complex

A necessary compromise

Under the hood, games are intricate pieces of code that take years and years to develop. Whether it's your favorite indie title or the next big AAA behemoth, modern games generally need significant developmental resources to come to fruition. One reason why we still see games relying heavily on single-core performance is that it's far more complex to write code that allows games to utilize more than a few cores effectively.

First, game developers need to devote already limited resources and time to figuring out how to distribute various game operations across multiple cores. Second, some tasks just cannot be "parallelized" to a degree where the benefits would make the process worth it — keeping everything in line across multiple threads often introduces significant overhead and problems with scalability. Third, game developers often try to target the lowest common denominator for widest usability, instead of prioritizing game optimization for high-core-count CPUs.

Combined with other factors (some of which I'll discuss in the next sections), this makes it easier to focus on single-core performance, and optimize games to fully utilize a single CPU core. Hence, when monitoring in-game utilization, you'll often see the primary CPU core being loaded the most, followed by relatively low utilization on the rest of the cores. Depending on the workload at hand, the "primary" core can change from one to the other, but the point remains that most games are still dependent on the performance of a single core.

Game engines still don't utilize multiple cores enough

Parallelization doesn't come easy

Another reason why you'll see many games fail to properly load multiple CPU cores to a great extent is linked to the underlying game engine. Although there are dozens of game engines that developers can theoretically choose from, it usually comes down to a handful of options. Developers created many of the most popular game engines long ago, some in the 90s, at a time when they weren't designed to use multiple cores.

However, despite the fact that their modern iterations have received support for multiple cores, game engines haven't been able to incorporate parallelization to a great extent. Many game tasks are still designed to run efficiently on a handful of cores. Considering the industry is consolidating into a few game engines that haven't yet significantly leveraged multiple CPUs, it'll be a few years before we see multi-core CPUs really benefit games, at least outside a few demanding titles.

Modern games are heavily GPU-bound

Gaming load isn't distributed equally

Lastly, most modern games are designed in a way that the graphics card ends up doing the heavy lifting. GPUs are great at performing parallel processing, meaning they can simultaneously perform a massive number of similar calculations. This makes them ideal for tasks such as vertex processing, rasterization, fragment shading, lighting, some particle physics, and ray tracing.

Although handling AI decision-making and decompressing game assets still falls to the CPU (unless DirectStorage is used), the GPU is still the major driver when it comes to rendering games with complex and demanding visuals. Hence, it often makes sense for the developers to prioritize optimizing for the GPU instead of devoting resources to leveraging additional cores of the CPU.

You likely have seen many PC builders compromising on CPU power in favor of a more powerful GPU. When the majority of the gaming load is borne by the GPU, gamers deem it natural to spend the bulk of the budget on the graphics card. AMD's 3D V-Cache has done wonders for CPU-enhanced gaming performance, and Intel is expected to follow suit, which could slowly translate to multithreaded tasks benefiting more from an additional L3 cache. However, as it stands, the dependency of games on the GPU isn't going to soften anytime soon.

You still need a modern CPU for optimal gaming performance

Despite modern games not being able to fully utilize multi-core CPUs, you need to have a modern 6-core CPU (at least) on your gaming PC to avoid holding back your GPU. The CPU is essential for several AI and physics-based calculations in games, and if it isn't able to keep up with the graphics card, you'll end up with suboptimal performance.

There still are some demanding titles that can stress modern CPUs more than others. Moreover, for simulation, RTS, and competitive titles, having one of the best gaming CPUs can benefit you a lot when it comes to achieving maximum FPS on your system.