When Should you Upgrade your CPU?

It’s the age-old PC gamer’s dilemma: You have one of the best graphics cards on the market, but the rest of your system is showing its age, so should you upgrade your CPU or not?

It might not come as a surprise that the answer is “it depends”.

While a CPU upgrade doesn’t usually have as great a gaming performance impact as a GPU upgrade does, it’s not unnoticeable. Besides, there’s more than gaming to consider– your CPU is the brain of your entire computer, after all.

To decide whether to upgrade, you need to figure out exactly what you want out of a CPU, and you need to know whether your current CPU is still up to the task in modern games and applications.

What does the CPU do?

The CPU (central processing unit) is like the brain of the computer. It computes all the instructions that are given to it by your operating system and programs, although it does delegate some tasks to other components.

Modern CPUs have multiple ‘cores’, which can be thought of as individual CPUs in their own right, which perform operations simultaneously. CPUs also run at a certain ‘speed’, measured in MHz (megahertz) or GHz (gigahertz), often ‘boosting’ up to higher speeds when needed.

CPU vs GPU for gaming

Because your CPU is what runs all the instructions given to it by your operating system and applications, it affects every aspect of your desktop experience arguably more than any other component. As an upgrade to the ‘brain’ of the computer, a CPU upgrade should improve all aspects of your desktop experience, not just gaming.

A GPU (general processing unit), however, only works on things like graphics rendering, which makes having a powerful one important for specific things like gaming and animation software but less important for most general-use apps. For these specific use cases, though, a graphics card upgrade should give you a much bigger performance uplift than a CPU upgrade.

Deciding whether to upgrade your CPU or GPU largely comes down to how important you find gaming or using render-heavy applications. If you want to increase your in-game FPS, a GPU upgrade will likely be the better choice. But if you want to improve your day-to-day desktop and app performance, you might be better opting for a CPU upgrade.

CPU Cores for Gaming

Games have always been much more reliant on a CPU’s single-core performance than its multi-core performance. Single-core performance refers to how fast your CPU’s individual cores can compute instructions, whereas multi-core performance is how fast your CPU performs operations that utilise multiple cores.

This has started to change over recent years, but not dramatically so. Older games shouldn’t need more than four cores to run optimally, but newer games have started utilising six cores very well, which means having a six-core CPU should make the most of today’s games. Having more than six cores is usually overkill if gaming is your primary concern, though.

On the other hand, if you see yourself undertaking heavy productivity tasks like video editing, the more cores your CPU has the better.

CPU Speed for Gaming

Because a CPU’s single-core performance is still more important than its multi-core performance for gaming, its speed is often more important than its core count.

A CPU’s clock speed is measured in MHz (megahertz) or GHz (gigahertz), which measures how many ‘cycles’ of transistor toggling your CPU can execute per second. The more cycles per second, the more calculations it can perform each second.

But a CPU’s overall speed doesn’t just come down to its clock speed, because how the CPU is designed can also affect how many instructions it can complete each second. For this reason, the number of instructions per clock (IPC) that a CPU can perform is also important.

Regardless, it’s difficult to know how quickly a CPU will perform different tasks without actually seeing it perform these tasks, which is why it’s best to look at real-world benchmarks and reviews to see whether a CPU is worth purchasing.

How to Check CPU Performance

So, you know what to look for in a CPU, but to decide whether to upgrade you also need to know how this compares to your current CPU’s performance. The best way to do this is to run CPU benchmarks and CPU-intensive games and compare your results to CPU benchmarks online.

But you might also want to know whether your CPU is holding your system back by bottlenecking your other components, because if this is the case then you’ll know you need to upgrade without having to compare it to other CPUs at all.

What is a CPU Bottleneck?

‘Bottlenecking’ refers to when one component is capping your PC’s performance and the rest of the system would be capable of performing better if this one component were upgraded. A CPU bottleneck is when your CPU is acting like the neck of a bottle, preventing the rest of your system’s power potential, the metaphorical liquid in the bottle, from pouring out quickly and being realised.

For instance, if you have a great graphics card but a weak CPU, your CPU might not feed data to the graphics card as fast as it could theoretically handle. In this case, your graphics card wouldn’t be being used to its full potential because the CPU would be artificially capping its performance.

If your CPU is bottlenecking your system in this way, it might be time for an upgrade.

How to Test for a CPU Bottleneck

To test for a CPU bottleneck, you need to find out how much of your CPU is being utilised while running apps and games and compare this to your GPU’s utilisation.

To check for a bottleneck, it’s better to run games that you play and apps that you use rather than running CPU benchmarks and stress tests. CPU benchmarks and stress tests often try to max out your CPU’s load, meaning they’ll always show close to 100% CPU utilisation.

By running games and apps that you use, you get a more accurate picture of your CPU’s day-to-day utilisation and whether it’s bottlenecking your system. If your CPU is at, or just below, 100% utilisation while playing games, and if your GPU isn’t close to maxing out on utilisation, then you know that it is likely bottlenecking the rest of your system while gaming.

To check your CPU’s utilisation, you can use a program like HWMonitor, which should show all your CPU cores’ utilisation percentages in a separate sub-section.

If you don’t have HWMonitor downloaded, however, you can use Windows Task Manager to monitor your CPU’s utilisation.

Press Ctrl + Shift + Esc to open Task Manager, navigate to the ‘Performance’ tab, then select CPU. You should now see a graph showing your CPU’s utilisation percentage. Right-click the graph, hover over ‘change graph to’, and select ‘logical processors’. This should show the utilisation of all your CPU’s cores and threads.

Now, boot up some of the most CPU-intensive games you own and see what those graphs look like while playing. This is my CPU utilisation while playing the Overwatch 2 beta:

One thing to note is that having one or two cores close to 100% utilisation is not uncommon and is only a problem if your CPU doesn’t have many more CPU cores than this. And while it’s useful to look at individual core performances, you should also keep your eye on your CPU’s total utilisation percentage underneath the graphs.

It should be obvious if your CPU is bottlenecking the rest of your system. You’ll notice that your GPU utilisation (on the left-hand side of Task Manager’s Performance window) isn’t close to maxing out, while your CPU utilisation is maxing out on most of its cores. Given that most modern games utilise about six cores, if six or more cores are at max utilisation when you play games, then you likely have a CPU bottleneck.

When Should you Upgrade your CPU?

If your CPU is bottlenecking your GPU or other components, you should consider upgrading. You should monitor your CPU and GPU utilisation while gaming in Windows Task Manager to check this.

Your CPU will likely be bottlenecking other components while gaming if it has less than six cores, given that most games utilise six cores these days. However, for some games four cores is still sufficient.

You should consider more than just gaming, though. If you use CPU-intensive applications, such as for professional editing, then it’s usually worth upgrading your CPU every two or three CPU generations. Similarly, if you’re running a very old CPU you might want to upgrade just to improve your day-to-day desktop experience.

You should also consider whether you need the latest technologies associated with a CPU upgrade. For example, if you want the latest PCIe and DDR standard capabilities you’ll need a modern motherboard and CPU combo.

A good rule of thumb, however, is that if you have a current- or previous-gen Intel or AMD CPU with six cores or more, upgrading your CPU likely won’t give you a big gaming performance uplift. If your CPU is a few generations old or has less than six cores, however, and if you already have a good graphics card, then upgrading your CPU should give you a noticeable performance boost.