CPU and GPU Bottleneck detailed and easy explanation

CPU and GPU bottlenecking

CPU and GPU Bottleneck

If you’re into PC gaming, I’m pretty sure you’ve heard the terms CPU and GPU bottleneck. And obviously, if you are into PC gaming and have to know about CPU and GPU bottleneck. Now, you’re here because you do not fully understand what the CPU and GPU bottleneck is. And want to learn what exactly it is? Why does it happen, and what is wrong with it? How to identify if you’re experiencing it? And how to fix the bottlenecking issue?

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Well, that is what I’m going to be covering in detail. So let’s get to it. Before talking about CPU and GPU bottleneck, let’s first understand what bottlenecking is.

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CPU and GPU Bottleneck: What is Bottlenecking? And where does the term is come from?

In simple words, the bottleneck is just the neck of a bottle. When you’re pouring a liquid out of a bottle and a glass, you’ll notice the glass water came out more quickly as compared to the bottle. That is happening because the narrow neck of that bottle restricting the flow and limits the amount of water to go out. On the other hand, the glass mouth completely open, and there is nothing that can restrict the water flow.

cpu and gpu bottleneck
CPU and GPU bottleneck

But, what does that have to do with CPUs and GPUs? Well, the CPU and GPU work together to run games. CPU takes the data, processes it, and feeds it to GPU. If there is a huge difference in input and output data, the bottleneck will likely happen.

CPU Bottleneck

Now switch over to our gaming PC. Instead of water, of course, what we want is as many frames per second flowing from our graphics card as possible. We don’t want to have anything that restricting our graphics card from it being able to do its job to its absolute potential. Now to run the GPU at its full potential, we need the CPU to be fast enough that can process and deliver the data such as keyboard input, mouse input, game actions, game assets, game physics, UI, audio, etc to the graphics card.

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The faster the CPU processing the data and send it to GPU, the faster the GPU does its job and resulting in more frames. Ideally, you want your CPU to feed raw commands to your GPU as fast as your GPU can produce new frames. You want to have your GPU utilization at 100%. That means the GPU is working as fast as it can and outputting the maximum number of frames.

If your CPU isn’t powerful enough to processing data and send that data to the GPU on time, the GPU ends up sitting idle for fractions of a second. Means your GPU will output fewer frames per second even though it’s capable of more fps. This is called a CPU bottleneck because your CPU is restricting or slowing down your GPUs performance.

Example of a CPU bottleneck

A perfect example would be if you pair GTX1660 with AMD A10 5800K. 

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cpu bottleneck
CPU bottleneck

In this benchmarking footage from Shadow of the Tomb Raider at 1080p, a GTX 1660 paired with an AMD A10 5800K, which is a pretty old and pretty underpowered CPU by today’s standard.

As you can see here, the CPU utilization is at 100% but, the GPU utilization is between 50% and 70%. The CPU is running at its maximum performance. But, it is unable to send raw commands to the GPU fast enough. This results in the frame rate being in the 30fps-40fps.

Now, pair the GTX1660 with a Ryzen7 2700X with the same graphical settings. 

cpu bottleneck fix
CPU bottleneck fix

We see the GPU utilization pretty well max out at 98%. And the CPU utilization stayed much lower than before at around 20-30%, giving us a consistent 60 plus frames per second.

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GPU Bottleneck

So what about a GPU bottleneck? Well, it’s the same concept as CPU but another way. Meaning the CPU is fast enough to process data and feed to GPU. But the GPU itself is not fast enough to handle the incoming data to process.

Well, unlike a CPU bottleneck, a GPU bottleneck isn’t necessarily a bad thing. When it comes to gaming, it is what you want to have. A GPU bottleneck occurs when your GPU is running at 100% utilization, but your CPU is not.

gpu bottleneck
GPU bottleneck

Just like the above benchmark, the GPU is running at 100%. But the CPU is far from that. In this scenario, the CPU is processing the game really fast. But the GPU can not handle that amount of data to process quickly. Sometimes it is good. Because it means my GPU isn’t being slowed down. But, it also means the graphics card can be upgradable without worrying about CPU bottlenecking.

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Causes of CPU and GPU bottleneck

So why CPU and GPU bottleneck happens? As I said earlier, either a slow CPU or slow GPU could be the main reason. But that is not always the case. CPU and GPU bottleneck can depend on games to games. There are such games that mostly either CPU or GPU-dependent.

Games that usually have a high frame rate even though the GPU the low-end are considered CPU-dependent games. Such as Minecraft, AC: Black Flag, etc. On the other hand, the games which frame rates differ with the different graphics card usually fall under the GPU-dependent category. These are also the games that demand a better graphics card for a decent performance. Also, these games have better and realistic graphics.

How to identify CPU and GPU bottleneck?

To identify whether the CPU is bottlenecking or the GPU, you can use utility software like MSI Afterburner and Riva Tuner(Riva Tuner comes with the afterburner, so you don’t need to install both separately) to monitor the usage of different components of your PC.

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Here are the steps to monitor hardware usage and game frame rate.

Step1:

Download the MSI afterburner. Install and open it. When you start Afterburner, Riva Tuner starts automatically.

Step2:

Riva tuner
Riva Tuner

First, on the Rive Tuner window, turn on the Show On-Screen Display.

You can also turn on start with Windows, so you don’t have to do this every single time when starting your PC.

You can play with other options to customize it if you wish.

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Step3:

On the MSI Afterburner window click on the settings icon.

Step4:

Click on the Monitoring tab.

Step5:

Msi afterburner
MSI Afterburner

Under the “Active hardware monitoring graphs“, you can see the list that you can monitor while playing games. Such as GPU and CPU temps, GPU usage, CPU Usage, etc.

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Just click the left side of the list item to enable the monitoring.

Step6:

Click on Show in On-Screen Display under GPU temperature graph properties.

Step7:

Click Apply and hit OK.

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Eliminate CPU and GPU bottleneck.

If you are experiencing a CPU bottleneck, unfortunately, there’s not really anything you can do to fix it outside of upgrading to a more powerful CPU. 

Although you can apply these options to increase CPU performance as much as you can. 

  1. Increase the in-game graphics setting so the GPU will take time to render the game.
  2. Stop unnecessary software that uses CPU in the background.
  3. Overclock the CPU. Overclocking CPU can increase a little bit of performance.
  4. Overclock the RAM. Overclocking the RAM can give a boost in performance.

On the flip side, if you’re experiencing a GPU bottleneck, overclocking GPU can increase its performance a little bit. Or decreasing the in-game graphics settings.

If your GPU is bottlenecking, you have the option to upgrade your graphics card without even needing to upgrade the CPU.

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