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What is a CPU? A beginner’s guide to processors

The term CPU may be best known in the computing industry, but they’re actually used in a wide variety of devices including smartphones, tablets, games consoles and even your TV.

But what exactly is a CPU, and why is it so important? We’ve created this detailed guide to explain everything you need to know, as well as what to look out for when making a purchase.

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What is a CPU?

The CPU (Central Processing Unit or simply processor) is the main chip in an electronic device that is responsible for managing and sending instructions to other components. It’s best to think of the CPU like the brain of a device.

CPUs exist in many different types of devices. If something can run programs (via an operating system such as Windows, Android or iOS) chances are it will have a CPU. For example, both phones and TVs have CPUs inside them.

In modern computers, and especially in smartphones, the CPU may sit on the same physical chip as other components. Most modern computer CPUs share a chip with a computer’s graphics electronics which is responsible for generating images (including something as simple as text or colour) on a screen. Many CPUs now also host an NPU, which allows a device to benefit from AI-powered features.

In smartphones and tablets, the chip containing the CPU may also handle phone calls, Wi-Fi, GPS and many other things. Such multi-purpose chips are known as SoCs (system-on-a-chip).

Snapdragon 810
Mobile SoCs contain a CPU and loads of other important kit that makes your phone work

What are the functions of the CPU in a computer system?

The CPU is involved in pretty much every task a computer will undertake, as it’s required to send instructions to every component in your PC. Without a CPU installed, your CPU simply wouldn’t turn on.

For example, while it’s the GPU‘s job to generate images, it wouldn’t be able to do so without the instructions sent by the CPU. This means that they work in tandem with each other, and is why you can have CPU ‘bottlenecks’ when gaming, even if you have the most powerful GPU available.

Not every CPU is the same, as they will differ in the speed that it takes to send messages which will affect how long it will take to complete tasks from opening a new tab on Google Chrome to editing a 4K video.

The clock speed of a processor will determine how many instructions a CPU can make each second, while increasing the number of cores and threads allows the CPU to carry out a greater number of tasks simultaneously without slowing down.

Where is the CPU located in a computer?

In a computer, the CPU is found at the heart of the system, plugged directly into the motherboard. You wouldn’t be able to see it if you took the side panel off your desktop PC, as it will be hidden under a cooling fan – a CPU is a powerful component and would get very hot without proper cooling.

In a desktop PC, the CPU and cooler are designed to be easily removable. This means replacing a processor is a relatively simple process. It doesn’t mean a processor can be easily swapped for a more powerful model, however, as the CPU will need to be compatible with the motherboard.

Intel Core i9-13900K CPU
Intel CPU installed on a motherboard – Image Credit (Trusted Reviews)

Most of the time, if you’re upgrading to a CPU that’s a year or two newer than your current one, you’ll also need to fit a new motherboard.

In laptops (as well as smartphones and tablets), on the other hand, the CPU and cooler are as good as impossible to remove (and even harder to replace). It’s not possible to change the motherboard either, so it’s best to think of laptops as non-upgradable in this regard.

Which CPU should you buy?

If you’re looking to upgrade the performance of your desktop PC, then buying a new CPU is worth considering. Of course, which CPU you should buy is dependent on what kind of workloads you plan on giving your computer.

Most people will be perfectly fine with a mainline Intel Core or AMD Ryzen processor. For basic web browsing tasks, an Intel Core i3 or AMD Ryzen 3 processor is a good value option. For gaming purposes, you’ll want to buy an i5/i7 or Ryzen 5/7 processor, while those who want to engage in complex tasks (such as 4K video editing and 3D animation) will potentially need to look at an Intel i9 or AMD Ryzen 9 processor.

It’s also important to factor in the generation of a processor, with a larger number indicating a more recent launch. For example, Intel Core 14th generation CPUs are generally more powerful than Intel’s 10th generation.

You won’t want to buy a chip that’s too old, as it could be outdated and lacking the performance punch required for modern tasks, but you find great value options by looking for a chip from the previous couple of generations.

We always recommend checking out reviews before purchasing a new CPU, or even checking out buying guides such as our Best CPU, Best Intel Processor and Best Gaming CPU round-ups. The specs sheet can give you a lot of information about a processor, but won’t paint the whole picture of real-time performance.

CPU Jargon Buster

There is a vast difference in computing performance between different models of CPU. PC and laptop manufacturers tend to splash three things all over their marketing material when trying to sell you a computer: clock speed, cores and threads.

We’ve included a quick summary of all the most common CPU jargon, providing brief explanations for each one:

Clock Speed

Clock speed is expressed in gigahertz, or GHz, and is a rough indication of how many calculations a processor can make each second – the higher the number, the more calculations. This is one of the most important considerations for a gaming performance, with a high clock speed generally more important than hacking lots and lots of cores.


How quickly a CPU can process data is also affected by how many cores it has. Each core is essentially a CPU in itself, and many programs are written so that multiple cores can work on processing the data the program requires at the same time – vastly increasing how quickly that program can run.

Modern CPUs have at least two cores, with many having four, eight or even more. Having multiple cores will certainly give you a speed boost, but it depends on the kind of program you’re running: a quad-core processor can perform some tasks, such as video editing, almost twice as fast as a dual-core chip, but adding more than four cores won’t necessarily improve the gaming performance further.


A CPU thread is essentially a virtual version of a CPU core, which helps to make a processor’s performance more efficient. These days, AMD and Intel processors will typically have two threads per core but this isn’t always the case.

Like cores, having a high thread count is important when your computer is multi-tasking or dealing with heavy workloads. Top-end AMD Ryzen processors usually have high core and thread counts, so it’s worth looking at those chips if a high core and thread count is priority.

Intel Core 13th gen Raptor Lake
Credit: Intel

Which companies make CPUs?

There are four different major mobile processor manufacturers right now. They are as follows:


Team Blue develops a large variety of mobile processors, from m3 CPUs typically found in low-performance Chromebooks, to i9 Intel Core chips that can power beasty gaming and content creation machines.

Intel often offers the most powerful desktop processor, especially for gamers, and also dominates the laptop market with its vast range of processors. If you own a Windows PC or laptop, there’s a good chance it’s powered by Intel.


Team Red is the closest competitor to Intel, also offering a wide variety of mobile CPUs. AMD offers C-Series and Athlon chips that are specially designed for Chromebooks.

Ryzen chips are found in more high-end laptops, from ultra-portable productivity machines to powerful gaming systems. AMD mobile processors are still less common than Intel chips, but we’ve been impressed with Ryzen’s performance and battery efficiency in recent years.

Qualcomm Snapdragon

The Snapdragon CPUs are more well known for being housed inside Android smartphones, but they’ve recently started to become more common in laptops.

Using Arm architecture, the Snapdragon chips typically offer a low performance, but boast fantastic battery life. Expect to find these processors inside mid-range laptops focussed on portability rather than inside powerhouse machines.

Apple Silicon

The newest challenger in the mobile processor market is Apple, as the company decided to start developing its own laptop processors for MacBooks instead of relying on Intel.

Apple has been creating its own CPUs for MacBook since 2020, and so has a few years under its belt so far. Apple’s M chips offer incredibly good power efficiency, resulting in far better battery life than laptops powered by AMD or Intel instead. The M chips have also been very competitive with AMD and Intel rivals in terms of performance power.

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