CPU

Here's everything you need to know about that clever little Central Processing Unit (CPU) inside your PC.

The CPU is the brains of the PC (and most electronic devices) and is responsible for carrying out calculations and handling pretty much anything that requires processing power. It's made up of various internal components that work together to execute a string of stored instructions, which are repeated in cycles. But really all you need to know is that it handles everything you need to do on a day-to-day basis.

When looking at purchasing a CPU, it's worth keeping in mind various factors such as clock speed, core count, socket type, and component support. Here's everything you need to know to make a smart purchase.

Team red and blue

Intel

The two major players in the PC CPU market are Advanced Micro Devices (AMD) and Intel. Both companies have been producing chips for desktops and notebooks for decades and are similar in many ways. For the average user, installing an Intel or AMD CPU in a supported motherboard will achieve similar results — you'll be able to run Windows 10 without much issue.

Especially with the release of Ryzen, AMD's latest generation of processors, there's very little to separate the two brands, aside from slight fluctuations in pricing, performance, and reliability. On the side of AMD, you have Ryzen, and with Intel, you have the Core and Xenon line of performance-driven CPUs, as well as the Celeron, Pentium, and Atom families for more affordable builds.

Here's how they stack up (in ascending order of performance):

AMD

  • APU (previous generation)
  • FX (previous generation)
  • Ryzen (3, 5, 7, 9)

Intel

  • Celeron
  • Pentium
  • Atom
  • Core (3, 5, 7, 9)
  • Xenon

This is where things can get a little confusing, because not only do you have multiple families of processors to choose from each company, but there are multiple models within each family with different numbers of cores, threads, and speeds.

Sockets and chipsets

CPU

Not all CPU generations are created equal. There are different configurations of contact pins, which connect the processor to a motherboard. When inserting a CPU into a socket, these pins are used to transfer data to and from the main board. Both AMD and Intel use a select number of these pins, which are then designated as a socket. Sockets are named to dictate how many pins are present. (LGA 1151 has 1,151 pins, for example.)

This is also why it's recommended you do not come in contact with the underbelly of a processor (or the contacts on a motherboard) since these parts are incredibly sensitive and important. It's also why you should carefully consider the socket, based on future upgrades. The next line of processors may not be compatible, requiring you to purchase a new motherboard. However, a socket is generally compatible with a number of CPU generations, depending on how Intel and AMD work on product iterations.

AMD sockets

The new AM4 socket (also known as PGA 1331) has a total number of 1,331 contacts and was launched alongside the latest iteration of Ryzen processors. It's the only AMD socket you should really be concerned with, as older FX processors don't work with the socket and you really shouldn't consider these CPUs anyway, considering how value-friendly the new Ryzen family is.

This socket is supported by the following chipsets:

  • X370 — The most advanced option with SLI and CrossFire, overclocking and eight PCIe 2.0 lanes.
  • B350 — Mainstream chipset with overclocking and six PCIe 2.0 lanes.
  • A320 — Entry level and affordable with no support for overclocking.

X300 and A/B300 are for small-form-factor PCs and can be ignored unless you wish to build a low-power device.

Intel sockets

Intel is where things become a little more interesting. AMD Ryzen is still new and so there are only a few chipsets available for a single generation of processor. Intel has a number of chipsets for multiple generations of supported CPUs. It can get a little hectic when you're looking at sockets and supported chipsets. Usually, you're going to choose between CPUs that use LGA 1151, or LGA 2011 if you wish to spend the extra bucks for more advanced hardware.

The latest chipsets for Intel can cause confusion, especially with the latest "Coffee Lake" CPUs not being supported by 100 and 200 series — the former launching with "Skylake" and the latter with "Kaby Lake." Both Skylake and Kaby Lake CPUs can be used interchangeably with 100 and 200 series motherboards, but not the new 300 series chipsets. Intel changed some things with the layout of the socket for the new processors, so backward compatibility is not possible.

Kaby Lake

This family of chipsets supports both Kaby Lake and Skylake CPUs, but not newer Coffee Lake units.

  • B250
  • Q250
  • H270
  • Q270
  • Z270

Coffee Lake

As aforementioned, this chipset series only supports Coffee Lake CPUs.

  • Z370

When it comes to choosing a CPU, socket, and chipset, start with the processor itself. Once you've decided on the CPU, the socket and available chipsets will be filtered to make the whole process much easier. For example, going with a Core i5-7600K, I would recommend the H270 for mainstream use or Z270 for gaming and more enthusiast builds. Motherboards list available features, allowing you to effectively compare between chipsets.

Cores and threads

AMD

Processors handle instructions in cycles, and to allow a single chip to handle more instruction sets simultaneously, Intel and AMD (as well as other CPU vendors) employ what is known as "cores." Think of a core as a CPU and multi-core processors as multiple CPUs fused together. This allows for more data to be processed at any given time, should software be coded to take advantage of this feature.

The recommendation in new PC builds is to go for a dual-core CPU at the very least with quad-core CPUs the ideal option for future proofing and performance, though more cores don't immediately result in increased performance. But as well as cores, you should also consider threads. Multi-threaded cores allow the processor to further divide its resources to handle two executions at once. A single-core processor will have a single thread, a dual-core processor two, dual-core processor with multi-threading four, and so on.

Depending on what you plan to do, more cores may be more efficient than more threads. Gaming in certain titles may take advantage of physical cores, while video editing and intense applications may favor hyperthreading. It's worth doing a little research, but overall you really cannot go wrong with a quad-core hyperthreaded CPU like an AMD Ryzen 7 or Intel Core i7.

Lastly, you should consider the speed of the processor. This is measured in megahertz (MHz) and gigahertz (GHz). Bearing CPU cycles in mind, a single MHz indicates a million cycles per second and a GHz a billion cycles, so looking at a 3.4 GHz processor means it will be able to handle just shy of three and a half billion cycles per second. That's a lot of processing power.

Choosing the best for you

There are a number of options out there that match different budgets and requirements. It's worth doing a little research on processors to see which offers enough power for your needs and then work from there to put together a build with compatible components. If you're truly stumped, we rounded up the best CPUs for a custom PC, which will help get you started.

Best CPUs for your custom PC