The performance of a computer is not always as simple as getting the best graphics card, and the best CPU. If there’s a mismatch in the performance of
A GPU can bottleneck a CPU. If the GPU is faster than the CPU it will be sitting idle waiting for the CPU to load. This is an example of an inefficient computer. The most efficient computer will have a CPU and a GPU that have similar relative performance so neither is waiting for the other.
There is a range of different programs and ways of using a computer. Such as gaming, Photoshop, CAD, and video rendering.
So, below, I’ll provide an easy-to-understand explanation about what causes the GPU to bottleneck a CPU, so you can get a very clear picture about if it can occur when using a computer in general, and for each of these more specialized uses.
When Is a CPU Bottlenecked by the GPU?
The way computers are designed means that the CPU and GPU can be out of sync. This causes delays between data being sent from one component to the other and results in what’s called a bottleneck. Below, is a summary of how a CPU is bottlenecked by the GPU specifically.
A CPU is bottlenecked by the GPU when the CPU is slower than the GPU. If the GPU is faster it will complete its task before the CPU can send further instructions. At this time the GPU is doing nothing and is ‘bottlenecked’ by the CPU.
The opposite is also true if the CPU is older than the GPU. But, in that case, the GPU is bottlenecked by the CPU. A bottleneck occurs whenever one component is faster than the other.
The way computers work is that they process lines of code one at a time. Each line of code is a set of instructions. A simplified version of how it works is that these are sets of instructions that tell the computer components what to do. Each line of code takes up memory space on the components.
And each component has a maximum capacity for memory. Once this memory is full, the component needs to wait for the line of code to be executed and removed from the queue – basically, it’s deleted. This frees up more space for another line of code. Which as I explained before is a set of instructions.
How bottlenecking of the CPU and GPU occurs (so you can avoid it)
The CPU has lines of code that it offloads onto the graphics card (GPU). The GPU then executes these commands. The CPU takes time to process and generate these lines of code. And the GPU takes time to process the lines of code.
If the GPU takes a long time to process the lines of code the CPU will need to wait with full memory and can’t process anything new. This means the CPU is essentially parked and can’t do anything. But, if the GPU is faster the CPU can send more info to it which frees up space for it to do more processing faster.
Therefore, anytime the GPU is full the CPU has to wait according to Intel. Therefore, there’s a balance between how fast the CPU is and how fast the graphics card (GPU) is. If the GPU is significantly slower than the CPU the CPU will be bottlenecked.
If the CPU is slower than the GPU the GPU won’t be doing anything. It will need to wait for the next set of instructions from the CPU. This causes the GPU to be bottlenecked. Because it’s stopped from doing anything until the CPU has finished processing enough to offload it onto the GPU.
How to ensure your CPU or GPU don’t bottleneck each other
You can look at example prebuilt PCs to get an idea of the specs that the CPU and GPU should have in relation to each other. Intel provides three good examples of the components of their prebuilt computer on this page of their official website. Scroll all the way to the bottom of that page to see them.
You can then compare the specs of these to the specs your computer has. Or, components you’re going to buy separately to make sure they’re not dramatically different as a ratio of each other compared to the prebuilt PCs.
For example, if your CPU is 10% better than the CPU of a prebuilt CPU, but your GPU is 40% better than the GPU for that same prebuilt computer this will cause the GPU to become bottlenecked.
The same is true if the CPU is 20% more powerful, just as an example, and the GPU has 20% less performance than the GPU of the prebuilt computer examples provided on that website, then your CPU will get bottlenecked as the CPU will need to wait for the slower GPU.
Can Your GPU Bottleneck the CPU in Gaming?
When playing graphics-intensive games the CPU and GPU are generally running at full capacity. Especially if the graphics settings are turned all the way up. However, here’s a summary of whether it’s possible for the GPU to bottleneck the CPU when gaming.
A GPU can bottleneck a CPU in gaming. If the GPU has inferior specs to the CPU it will load slower than the CPU. This requires the CPU to wait until the GPU has finished processing to send further instructions, as a result this ‘bottlenecks’ how fast the CPU can process logic operations.
This is because the GPU has a fixed amount of memory. As it performs the tasks assigned to it by the CPU the GPU memory empties out, and new instructions can be copied onto it by the CPU. When the CPU takes longer the CPU needs to wait until its memory empties, and during this time the CPU can’t process anything new.
Can Your GPU Bottleneck the CPU in Photoshop?
Photoshop doesn’t require as much computing power as some other processes a computer can do. But, when it’s rendering or processing a large file or big groups of files it can max out the CPU. This puts additional strain on the GPU and requires it to also operate at its maximum so below I explain if Photoshop can bottleneck the CPU.
A GPU can bottleneck a CPU in Photoshop. If the CPU is faster than the GPU, the CPU will need to wait until the GPU has finished before the CPU can send further instructions. During this waiting time, it can’t process as much as it could if the GPU could keep up.
There are minimum specs that a computer should have to run Photoshop as listed here on the official Adobe website. Provided your computer is prebuilt and has these specs the CPU or GPU won’t bottleneck each other. But, if you’re building a custom PC you need to make sure that the specs of the GPU and CPU are suited to each other so that both can keep up.
Can Your GPU Bottleneck the CPU in Video Rendering or Editing?
Video rendering generally takes a very long time even with a very fast computer. To make a computer run as fast as possible the CPU and GPU should ideally be bottlenecked. But, is it possible for this to happen when editing video and processing the edited files when you render it?
A GPU can bottleneck a CPU in video rendering and editing. This occurs if the GPU is slower than the CPU. A CPU sends data to the GPU that frees up space on the CPU for it to do more tasks. If the GPU takes longer than the CPU the CPU needs to wait with a full memory until the GPU has finished.
If the CPU and GPU are suited to each other the speed of the GPU will be able to keep up with the CPU, and it will work as efficiently as possible and only minor if any bottlenecking of the CPU or GPU will occur.
Can Your GPU Bottleneck the CPU in CAD Applications?
There is various software that you can install on a computer to create CAD models and work with CAD files. Autodesk and AutoCAD are some of the more well-known and used software. They can use quite a bit of the CPUs capacity so here’s the long and short of whether the GPU can bottleneck the CPU when you’re using CAD software.
A GPU can bottleneck a CPU in CAD applications. This occurs if the GPU isn’t matched to the CPU. This can occur in custom PC builds but is very unlikely in prebuilt computers. If the GPU is slower than the CPU, the CPU has to wait for the GPU which bottlenecks it.
As long as your PC meets the minimum system requirements to run the software and the PC is prebuilt the GPU should bottleneck the CPU. A prebuilt computer is one that is sold as one computer and not one you’ve put together by buying separate parts yourself.
However, if you did buy the components separately and build your own PC it should also be fine provided the CPU is on par with the GPU. Meaning they’re about the same specs. Refer to the section near the top of this article with the heading ‘How to ensure your CPU or GPU don’t bottleneck each other’, where I explain how you can tell.
I started building and fixing PCs in high school. After a couple of years of offering consultancy to a PC repair shop, I became the goto guy for all my acquaintances for PC/Laptop related buying advice or troubleshooting.