What is PC Bottlenecking?

In simple terms, PC bottlenecking can be described as a performance limitation caused by a specific component or other aspect of a system that prevents the PC from achieving its maximum performance potential.

Or, to use a visual, trying to pour out an entire bottle of liquid out through the narrow opening of a bottle – you’ve got a liter of water, you’ve got a liter-sized pitcher on the other side, but the neck of the bottle is restricting performance. Literally, a bottleneck.

A PC performs very much in sync. Many people know the GPU (Graphics Processing Unit) is primarily responsible for in-game framerates and other GPU compute tasks, but the CPU (Central Processing Unit) needs to process data quickly enough to “feed” it to the GPU. In general, the content in storage on your PC is stored on an SSD or HDD. That data is then transferred through system memory (RAM) to your CPU and GPU. Thanks to the PCI Express bus, this data and system memory is accessible at extremely high speeds.

However, if your CPU is too slow to effectively sling data over to the GPU, then your GPU could be “bottlenecked”, meaning it has untapped performance. It’s just sitting around waiting for the next CPU cycle to complete. All that delicious data, the high-resolution game textures, the incredible game content, is sitting there in storage or system RAM, while the CPU tries its best to shift it. Heart breaking stuff.

Alternately, if your CPU is a powerhouse just tossing massive amounts of data out every cycle, but the GPU isn’t fast enough to handle them, the GPU will be your system’s bottleneck.

The CPU and GPU are the two most talked-about components, but they do not exist in a vacuum. On modern systems, system memory and storage can also play a part. For example, if you’re still using a SATA drive, you could be limited to speeds of around 500-550MB/s. While a modern M.2 NVMe SSD with PCIe 5.0 compatibility can produce sequential read speeds of up to 14,000MB/s. That’s about 25 times faster. If you have a modern high-end GPU and CPU, don’t bottleneck yourself with slow storage.

One of the other components that frequently gets overlooked is system memory, or RAM. RAM amount plays a large part in performance bottlenecking. For example, if you’re running high resolution modern games, you’re going to be swapping large texture files and huge amounts of data from storage to your GPU and CPU.

If you’re trying to do that with 4GB or 8GB of memory, you’re going to have a bad time. Modern systems perform best with at least 16GB of RAM, and some applications (like video editing programs) significantly benefit from 32, 64, or even 128GB of RAM. But the amount of RAM isn’t the only thing to think about – the overall bandwidth of your system memory, the frequency of the memory, can play a big part.

We’ve found that on modern systems, going from DDR5 4800 MHz to DDR5 6000 MHz can dramatically improve framerates.

For more information on why memory matters, check out our MEMORY MATTERS page.

If your memory is too slow, or you don’t have enough of it, you could bottleneck the rest of your system.

So now that we’ve established what bottlenecking is – what do we do about it? How can you tell if your system is bottlenecked and what do you do if it is?

There are several programs you can use to identify PC bottlenecks, but a couple of the more popular options are NVIDIA GeForce Experience or MSI Afterburner. These tools allow you to monitor your real-time CPU and GPU usage during games and benchmarks.

The system used for this test is an Intel Core i9 13900K processor with an NVIDIA GeForce RTX 4090, 64GB of CORSAIR Dominator Titanium DDR5-6400, and a 2TB CORSAIR MP700 M.2 NVMe SSD.

With the latest NVIDIA app installed, by pressing ALT+Z I can open the NVIDIA Menu, select “Statistics” from the bottom, then click “View All” which shows the statistics you can overlay on your PC.

What you want to select here is GPU and CPU Utilization, as they’re going to be the two most evident items that show where your bottleneck is.

Doing this produces an overlay that sits on the corner of the monitor and provides you with your system's frames per second, as well as the GPU and CPU Utilization %, like this:

Now, to run some benchmarks or games. Depending on what you’re trying to do with your system, this will change for you. If you’re concerned about bottlenecking during CPU intensive AI or Video Editing work, then you’d use different tools. You can use a number of reliable performance benchmarks, like CineBench, 3Dmark, PCMark 10, or others. Some games, like Shadow of the Tomb Raider, have built-in benchmarks that produce reliable scores.

Once you’ve determined which software you’re going to use for your benchmarking or performance monitoring, keep an eye on the GPU and CPU % numbers. What you want to look out for here is which component is consistently pegged at higher numbers. The item that has the higher utilization % is the item that is most likely to be the performance bottleneck.

In the examples in the table above, the GPU bottleneck would have the GPU constantly pegged above 95% while the CPU would be significantly lower, in this example, consistently under 70% utilization. This would imply the CPU is sitting around using very little of its capabilities while the GPU is using nearly everything it has. Conversely, if you swap those numbers, the GPU being under 70% utilization would imply it’s waiting around to do something, while the CPU being up around 95% or higher consistently would imply it’s doing everything it can, but still can’t keep up with the GPU. Note that these numbers are merely examples, and real-world numbers will look dramatically different.

Congratulations! You’ve found the piece of hardware that is preventing you from unlocking the full potential for your PC when it comes to running your favorite game or software. The next step is evaluating what to do. The easiest path to improving performance is to reduce settings. For example, in a game if you find yourself GPU limited, try adjusting the graphical settings down a notch or dropping resolution. On some cards, the driver software even has an “optimize settings” button that is specific to each game or software installed.

This option is free and can help you optimize graphical performance if your GPU is your bottleneck.

If you find yourself CPU bottlenecked, there are a number of options you can look into as well.

• Ensure your CPU isn’t overheating by monitoring temperature during benchmarks. If you find your CPU is overheating, follow troubleshooting methods for your CPU cooler to ensure it is installed and operating correctly.
• Make sure all your settings for your specific CPU are correct in your system UEFI/BIOS.
• Enable XMP (for Intel) or EXPO (for AMD) to ensure that your processor and memory are working at their rated speeds and that overclocking is enabled.

And lastly, there’s the priciest (but most fun) option: upgrade. The single best part of being a PC gamer is knowing that a number of items in your system can be upgraded individually. For a desktop PC, the options are nearly limitless. Even if your CPU is a couple years old, you might see a massive improvement by upgrading a graphics card. Need to fix that heat problem? How about a new CPU cooler. GPU overheating? Upgrade your case to a high airflow model with improved fans to keep it cool. Our webstore has a lot of options when it comes to PC upgrades, so take a look!

It's important to realize that every system has a bottleneck of some type for any given application. Whether that bottleneck is affecting your enjoyment of your PC is up to you. The difference between 30 FPS and 60 FPS is big, but between, say, 150 FPS and 180 FPS? That's up to you.