CPU Bottlenecking: What It Is And How To Tell If It's Affecting Your PC's Performance

A computer is a lot like an ecosystem. When all its components are functioning in a harmonious balance, a PC can whiz along at top speed, crunching calculations, booting games, and performing other tasks. But when one part of that environment is out of place, the entire system becomes unstable, and problems start to arise. In some cases, that happens because one of the computer's parts are mismatched with the rest, creating a weak point that brings the system screeching to a sluggish pace. This is commonly referred to as a bottleneck, and one of the most common items that can cause it is an underpowered CPU.

The term bottleneck is derived from the physical object it references. The neck of a bottle is the part where it narrows close to the mouth. Just as less liquid can pass through the neck of a bottle than through its wider body, a bottleneck in a computer system is the part of the computer with the least capability compared to the rest of the system. To use another metaphor, it is the weakest link in the chain. Any component in a computer can be a bottleneck. If, for example, you have the fastest possible GPU but an outdated CPU, then the CPU will most likely be your bottleneck because it will act like a slow worker in an assembly line, forcing everyone around them to wait. However, it is not considered a problem unless it prevents you from getting work done. And, of course, a slow computer has plenty of other explanations aside from bottlenecking. So, here's how to tell if your PC has a CPU bottleneck and what to do about it.

There are many different reasons for high CPU usage on a PC, and a bottleneck is only one of them. For instance, you could have a problem with your operating system or too many programs open. And a CPU isn't the only component that can cause a bottleneck, as a GPU, RAM stick, storage drive, and more are all able to be the lowest common performance denominator in a system. Therefore, if your computer is having performance issues, you need to isolate the problem to the correct component.

The easiest way to tell which component is causing a bottleneck is to run a graphics-intensive program and measure the performance of your system. The program could be a visually dense video game (for example, "Cyberpunk 2077"), but you could also try exporting a video from a video editor. Then, using Task Manager, check whether any component is running with 100% utilization. If so, it is most likely the bottleneck. More signs of a bottleneck can include low frame rates in games, even at low graphics settings, long loading times for programs and files, or higher

Additionally, you can run a bottleneck calculator. These are tools that will tell you, based on the specs of your computer components, which one is most likely to be the source of the bottleneck. They do not test your machine directly, instead using the known performance of your parts. They are helpful as a way of understanding whether your particular PC configuration is likely to have a bottleneck, but cannot determine real world causes such as a defective CPU.

If you manage to determine that your PC is, in fact, bottlenecked by its CPU, you will most likely need to upgrade the processor. Combining an underpowered CPU with a comparatively overpowered GPU is a lot like putting a sedan engine in a powerful truck  — even if the underpowered engine is brand new, it will have a hard time moving the truck. If the processor is functioning normally and is nonetheless a bottleneck in your system, you'll need to get a more powerful chip to solve the problem.

However, a malfunctioning CPU can often cause a bottleneck in a system that would otherwise operate within normal parameters. You can use a bottleneck calculator to determine whether the components in your system should function well together. If they should work on paper but there's still a CPU bottleneck in real world scenarios, there are a few possible solutions you can try before replacing your CPU altogether.

First, make sure your PC is thermally optimized, meaning it has good airflow and a cooling solution that can dissipate heat efficiently. There are many reasons your CPU can overheat, and since CPUs throttle when they overheat, this will lead to degraded performance. Cleaning your PC can stop overheating as well, and could remove debris that is silently damaging your CPU and its processing capabilities. Don't neglect the software side of things, either. Close all your running programs and see if the issue persists, and check for updates to your operating system, chipset, and drivers. You should also use trusted malware detection and removal software to rule out a virus or other threat. If all else fails, you can try reinstalling Windows, but that should be a last resort before simply upgrading the CPU.