CPU VS GPU – What is the Difference & How do you Avoid Bottlenecking

As gamers, we all want to run our games at 60 fps or more.

This means that your computer has to show you 60 shaders, shadows, and objects every second, which can be quite demanding.

So if you start to experience low frame rates in certain situations, it can be hard to know if it’s your CPU or your GPU that is causing trouble.

In this article, we will try to lay down the facts and look at how both units work and which parts of the game they each handle.

We will be doing this in somewhat broad strokes so that it is understandable even to the most technically impaired.

What is the Difference Between CPU & GPU?

Before going more in-depth on both units, let us take a broad look at the most significant differences.


The GPU handles the visual elements. Such as shaders, effects, shadows, light, textures, etc. The graphics card determines how many polygons that can be displayed at a time. It also significantly impact how high of a resolution any given object can have.

The GPU is the filter over the game. It handles the glowing effects, ability effects, light sources, etc.

The CPU handles the physical and logical elements. Such as hitboxes, logic(If-this-then-that-happens), movement, collision. It generates the in-game particles, in other words, it creates the world beneath the filter that the GPU creates.

You could say the CPU is the brain and the GPU is the eyes. Your brain understands the world, how it functions, physics, etc. While your eye is creating the images, you see in the world.

As an example. If you are playing a racing game and you collide with another car, then the CPU is the processor that knows what the logical outcome of this collision would be.

It is essential to understand that this is just in broad terms and there is more depth to it than this. As an example, GPU’s are critical for bitcoin mining and is more important than the CPU, despite having nothing to do with visuals.

However, when it comes to gaming, it is usually alright to look at the broad functionalities of the hardware as this is their general function within video gaming.

What is a GPU(Graphics Processing Unit)/Graphics Card

As stated earlier, the graphics processing unit determines the artistic side of the game and function as a filter over the base game.

When the game has generated bare polygons to make out objects, it is the graphics card that adds all of the ”graphics” essentially. This includes shaders, shadows, light, reflections, effects, and so on.

So the better the graphics card, the more polygons and higher resolution can be displayed at a time. So without the graphics card, your abilities in World of Warcraft would be simple boxes flowing through the air, same with your grenades and bullets in Counter-Strike, even your character.

Is GPU & Graphics Card the Same?

Yes and no, one does not function without the other. The graphics card is a chip on the Graphics processing unit, and they both enable each other to work. Since they are bought as 1 unit it is very common to refer to the GPU is the ‘Graphics Card.’ While this is not technically correct regarding terminology, it is easy to see why as you will never see a modern GPU without a graphics card.

What is a CPU(Central Processing Unit)

Image of processors for a PCWhile the GPU makes sure that everything looks good and polished, the CPU makes sure that the GPU has something to polish.

The Central Processing Unit handles the logical and organizational parts of the game. This includes objects, hitboxes, base particles. So in other words, the CPU is the part that understands how a solid object react to physical interference. Such as the wind blowing on a tree, a character being shot, etc.

As an example. Underneath the graphical aspects of each champion in League of Legends is the hitbox or the base polygons. This is the part you are aiming for and is what determines if an ability hits the target or not. This is why a spell in League of Legends can sometimes hit while it actually looks like it didn’t connect. The champion you see is just a filter and graphics, but the hitbox is the actual mechanics of the game beneath all that.

What is Bottlenecking – GPU/CPU Bottleneck Explained

Image of a PC bottleneckBottlenecking is a term used when a component is being held back by the restrictions of other factors. If you pour water from a wine bottle, it will flow considerably slower because of the bottleneck, hence the name.

When it comes to hardware, it is used to explain why your CPU or GPU might not perform very well due to restrictions from other hardware components.

Example: Let us say you buy a brand new 2000 dollar graphics card for your desktop. That would mean your graphics would improve right? Well, not necessarily. It depends on the rest of your specifications and hardware.

So buying a high-end graphics card and putting it together with a standard CPU or memory card will cause a bottleneck reaction. Meaning your brand new expensive GPU may only perform at a small percentage of it’s potential.

That is why you often hear people ask why they have low frame rates even though they just got a new graphics processing unit. Getting a new graphics card enhances your PC’s ability to create graphical effects better and faster, however, if you have a low-end CPU then the physics of the game won’t be able to keep up, and vice versa. Having a powerful CPU with a mediocre GPU will create the same problems.

CPU & GPU Overlapping

In the hopes of eliminating bottleneck issues, a lot of manufacturers is starting to implement CPU features into their GPU. This does not mean that you will get a good performance from a GPU alone but merely that the gap between GPU and CPU can be larger without causing issues.

Example: Some modern Graphics cards are also capable of handling physics to a certain extent. Such as the Nvidia PhysX, which can process some of the physical aspects of a game but that does not mean it can handle it alone entirely.

These modern GPU’s merely contribute to the CPU process and alleviate some of the bottleneck issues by carrying some of the CPU’s weight.

What is an APU(Accelerated Processing Unit)

Accelerated Processing Unit is the combination of the CPU and GPU in a single unit. This has some advantages and disadvantages. Let us take a look.

Advantages of APU

The fusion of CPU and GPU into one unit has some significant benefits in certain situations. First off, it eliminates CPU bottlenecking completely. While you can still have bottleneck issues because of your other components, this eliminates the most common and problematic type.

Secondly, it allows them to share ram which has many benefits concerning performance. Simply put, it makes it so that the single CPU and GPU units inside the APU perform better as they can borrow from each other.

Accelerated Processing Unit is handy for people who do not plan on upgrading the individual components of their computer. This is why both Xbox One and PlayStation 4 use APU instead of individual units.

Lastly, it is much more convenient, spacing wise. It takes up a lot less space which is why it is so prevalent in laptops and mini desktops.

Disadvantages of APU

APU’s are harder to swap out and if you like to keep your PC up to date with new hardware from time to time then separate CPU’s, and GPU’s are still the superior option.

APU is also believed to have worse longevity and durability, which might be why laptops and consoles tend to lose their performance capabilities faster than regular desktops.

Many of the very best GPU’s and CPU’s sold separately, and you won’t be able to find genuinely high-end performance with an APU, yet.

That being said, I do believe that APU will slowly take over the market within the next decade or so. As the more we learn about them, the more advantages they seem to have.

Image of CPU and GPU inside a computerBottom Line – Conclusion

You could say the CPU is the brain and the GPU is the eyes. Your brain understands the world, how it functions, physics, etc. While your eye is creating the images, you see in the world.

What is important is that you make sure that your hardware is relatively of the same quality as to avoid bottlenecking.

Please do not hesitate to ask questions regarding this topic in the comment section below.


  1. Thank you for the simple explanation. It really make me understand and will going to share with my students who play games. It will going to help them build their own rig.

  2. Thank you so much for the article; very informative
    What I really want to know is why GPUs have risen to such prominence recently. In the 80s, 90s, and early 2000s computers were synonymous CPU. So what was has changed. Essentially what are the benefits of using GPU versus a CPU. For example in driverless cars or mining’s
    Thank you!

    • Hi Ali,
      The rise in GPU’s is due to a few things but here is the main one:
      GPU’s can execute a TON more tasks at any one time, which is also why something like mining only works with a strong GPU since it requires a lot of multitasking from the processor.

      You can think of it like this:
      The CPU is the executive, it is able to do things that the GPU simply cannot but in terms of workload, it is inferior in most ways.
      GPU is the laborer, able to do an immense amount of work but often needs direction from the CPU. Will GPU’s can appear more powerful and effective for a lot of tasks I still wouldn’t recommend creating a set up without a proper CPU to oversee it all.

  3. Thanks so much for this excellent explanation. I especially like the example you use of a racing game, where the CPU figures out the physics of a car collision and the GPU figures out how to paint that scene (or the visual “filter” as you put it). This is such an easy way to understand the purpose of each unit and how they work together. You have a talent for this kind of writing — that’s very valuable!


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