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Is my CPU Bottlenecking my GPU?
Daniel Horowitz
|
January 18, 2023
Whether you are building your own PC or customising a new computer’s specs, it’s important to make sure that your CPU and GPU are of comparable quality. The GPU does not work in isolation and requires an equally powerful CPU to work properly.
In the case that you upgrade the GPU without upgrading the CPU, you may deal with CPU bottlenecking issues. But what is bottlenecking? And how can you prevent it from happening?
In this guide, we answer questions like “What is bottlenecking my PC?” and show you how you can avoid this nagging problem in the future.
What is CPU bottleneck?
A bottleneck occurs when a PC is running a demanding application and its performance begins to stall. Bottlenecks are a big issue in PC gaming, where the CPU is responsible for tasks such as performing input/output (I/O) operations, basic arithmetic functions, and running the game logic.
Those tasks are essential in more fast-paced games that require rapid information processing. Think of first-person shooters and real-time strategy games like the Total War franchise.
CPU and GPU struggles
When CPU slowdown occurs, it impacts the GPU, which cannot process the information fast enough, either. As a result, the GPU will struggle to render the game’s frames, leading to frame rate lag and a lackluster performance.
It is important to note that every system has some form of CPU bottleneck. It is impossible to have complete synchronisation between a CPU and a GPU. However, a game can only run as well as its slowest component allows, and it is important to know if the CPU is the component causing the bottleneck.
Monitoring your CPU and GPU
We recommend monitoring both CPU and GPU performance to test for potential bottlenecks. If a CPU load is higher than the video card's load by a significant amount, then your CPU is likely causing the issue. Fortunately, there are a number of tools that you can use to monitor your CPU and GPU.
MSI Afterburner
To directly monitor your CPU and GPU, you can use MSI’s freely available Afterburner software. Once you enable monitoring, you can get a feel for the software by playing a game impacted by bottlenecking issues. Then look at both the CPU and GPU usage.
If, for example, the game is utilising 80% of your CPU's capacity and only 30% of your GPU's capacity, then you can infer that the CPU is causing the bottleneck.
GPU comparison
You can also use the GPU Comparison tool from GPU Check. This CPU GPU bottleneck calculator allows you to plug in the model of your CPU and GPU as well as your desired graphics settings. Then, enter the GPU or CPU that you want to upgrade to.
The tool will then generate a report with more than a dozen comparative benchmarks. The one you want to look at is “CPU Impact on FPS,” which should be 10% or lower. This number will tell you whether a mismatch between CPU and GPU is causing a bottleneck, and whether upgrading either component will resolve the issue.
Fixing your CPU bottleneck
There are several ways you can lessen a CPU bottleneck’s impact. These include changing in-game settings, closing background programs, and overclocking your RAM and CPU. If all else fails, you can also upgrade your CPU to reduce your CPU bottleneck.
Increase a game’s resolution
One of the best ways to balance the load away from the CPU and onto the GPU is to increase your game's resolution. You can usually do this within the game’s settings. Higher resolution settings work to increase the number of pixels rendered by your GPU, which will put more of the burden of running the game on this component.
When increasing the game’s resolution, make sure that it’s not higher than your display’s resolution. You can find your screen’s resolution under the Display Resolution option under Display Settings. If you do increase a game's resolution beyond the screen resolution, it will have the opposite effect and actually reduce your frame rate.
Close out background applications
Background applications are one of the biggest culprits of a CPU bottleneck. A CPU typically runs at between 2% and 4% usage when idle, 10% to 30% when playing standard games, and up to 70% when playing more graphics-intensive games.
Those numbers assume that you close out of any other resource-heavy programs or applications when gaming. This includes the Google Chrome browser, which can eat up your computer’s resources, as well as music streaming services like Spotify.
You can avoid this by remembering to close programs you’re no longer using or by utilising the Task Manager. Within this program, you can close out any background applications to allow the CPU to focus more heavily on running the game. This should help to increase the game's frame rate and decrease CPU bottleneck.
Overclock your CPU
Overclocking your CPU can help to boost your PC's performance and decrease issues associated with bottlenecking. The only problem is that not all CPUs have the ability to overclock.
To check whether a CPU can overclock, see if yours has a feature called “unlocked multiplier.” All AMD CPUs, such as those in the AMD Ryzen™ line, have this feature, and many Intel® processors do, too. Intel adds the letter "K" to any of its CPUs that you overclock, such as the Intel Core™ i7-11700K.
Next, you should perform a CPU temperature check. You can do this with the Core Temp application. It allows you to easily monitor your CPU’s temperature at all times between multiple cores. Make sure that the temperature never rises above 176F° (80C°), otherwise you will damage your CPU and other PC components.
As you monitor your CPU's temperature, you can then safely overclock it. You can do this within the BIOS using the following steps:
- Go to Settings
- Select Update & Security
- Navigate to Recovery
- Choose “Restart now”
- After your computer restarts, select Troubleshoot from the menu
- Click Advanced options and then click on UEFI Firmware Settings
As you open the BIOS, you will need to navigate over to a setting called Advanced CPU Core Settings. You can manually adjust the CPU multiplier within this menu.
A good idea is to manually adjust the multiplier by one, and then reboot your computer to see if that helps with your CPU bottleneck. If not, go back into the BIOS and adjust it again until you can minimise the issue – within reason. Make sure you keep tabs on the CPU temperature fluctuations during the process.
Lower CPU-related settings
Another option for addressing CPU issues is within the in-game settings, primarily those that utilise the CPU. This includes lowering items such as population density, physics, vegetation, and draw distance, though these all depend on the game itself.
If you still don't see a noticeable effect by altering these settings, you can cap the game’s frame rate. Certain games will run at a higher frame rate than your CPU can handle. By using an in-game frame rate cap, you may see a reduction in input delay as well as a more stable frame rate.
Expansive single-player games, such as The Witcher 3, will also benefit from frame rate capping because all of the encounters and scenarios are pre-rendered. This allows the CPU time to catch up as the GPU renders the information into images.
Upgrade your CPU
If all else fails, it may be time to upgrade your CPU. This is important if your graphics card is too powerful relative to your CPU and they’re not in sync.
This often happens when you swap out your GPU to achieve better graphics without changing your CPU. In this case, upgrading your CPU will help to achieve more equilibrium between the two components, maximising game performance, graphics, and processing speed.
Before you upgrade, we recommend using the GPU comparison tool to see how your new CPU will work with your current GPU. Ideally, you want the load to be split as evenly as possible between the CPU and GPU to prevent your CPU from bottlenecking your GPU.
Summary
Identifying and fixing CPU bottlenecks may not be an easy task, but it’s not as difficult as you might think.
With the right tools and information, you can diagnose and treat the problem by changing in-game settings, closing extraneous applications, overclocking your CPU, or even replacing your CPU altogether. It’s also possible that some games will cause a bottleneck on your system no matter what, either because of their design or because of compatibility issues.
The best thing to do when encountering a CPU bottleneck is to start by changing in-game settings. The game may be running poorly due to how you have set it to perform.
While this won't always solve the problem, the majority of CPU bottlenecks are caused by poor optimisation. And the good news is that you can often fix this by making adjustments that work within your CPU’s performance capabilities.
