CPU BUYERS GUIDE

For gaming, the processor is rarely what decides your frame rate, your graphics card does that - the processor's job is to keep up, and the useful question is how much you need to spend before it stops being the thing holding you back.

There is one exception worth knowing before you choose - AMD's X3D processors carry a much larger cache - and that raises frame rates in games specifically rather than in benchmark scores. The rest of this guide covers what the model numbers mean, which specifications matter, and what your budget gets you. 

The central processing unit, or CPU, is the part of your computer that runs everything. It takes instructions from the operating system, from the programs you open, and from the games you play, works out what needs doing, and tells the rest of the machine to do it.

In a gaming PC it is not the part producing the picture on screen - that is the graphics card. The processor's job is to keep the graphics card fed with work fast enough that it never has to wait.

Processors have improved enormously over the last decade. A mid range chip today handles work that would have needed a high end one a few years ago, which is why the question is rarely whether a processor is fast enough, and more often whether it is the right match for the graphics card sitting next to it.

A CPU takes instructions and performs calculations, billions of times a second. At its most basic level the process has three stages: fetch, decode and execute. The processor fetches an instruction from memory, works out what it is, then carries it out using the relevant part of the chip.

On a modern PC the CPU does not do everything, but it feeds the components that do. In a game it works out where every object is, what the physics are doing, what the AI has decided, and where you are looking, then hands that to the graphics card to draw. If the processor cannot keep up, the graphics card sits waiting, and your frame rate drops even though the card itself has capacity to spare.

For gaming, the processor matters less than most people expect. The graphics card sets your frame rate ceiling, and beyond a certain point a faster CPU adds very little. What a slow one does is hold the graphics card back, so the job is to spend enough that it does not, and no more.

That point moves depending on how you play. At 4K the graphics card is doing almost all the work and a mid range processor is fine. At 1080p on a high refresh monitor, the processor is asked for far more frames per second and becomes the limit much sooner. Competitive shooters at 240fps are the clearest case.

Where a faster processor always earns its money is everything that is not the game. Streaming while you play, editing video, compiling, running background applications. Those are core count and multithreading jobs, and the graphics card cannot help.

Whether you are building from scratch or upgrading, the decision comes down to three things: what you do with the machine, what socket you are committed to, and how much of your budget the processor should take.

The sections below work through each of those. If you are upgrading, start with the socket, because that decides what you can fit before anything else does. If you are building new, start with what you actually do, because that decides everything else.

When choosing a processor, consider the following:

• Both AMD and Intel are competitive right now: Wth the current generation the difference between them is small enough that other factors, upgrade path, price on the day, what board you already own, will decide it for you. 
• For streaming, editing and rendering, core count matters more: These are the workloads where twelve or sixteen cores earn their money, and where the graphics card cannot pick up the slack.
• Budget for a full system: A strong processor paired with a weak graphics card will not make games run better. Work out the graphics card first and let the processor budget follow.

Spending as much as you can on the processor is the most common mistake in a first build. Past a certain point the money does nothing for your frame rate, and it comes out of the graphics card budget where it would have done a great deal. Define what the machine is for, then pick the processor that does the job. The bands below are a rough guide to what each level of spend gets you.

Around £80 to £130. For watching video, browsing, office work and light multitasking, an entry level processor with four or six cores is enough. Something like a Ryzen 5 5500 or an Intel Core i3 covers this comfortably.

Worth knowing: at this level you are usually pairing with integrated graphics or a very modest card, so the processor is rarely the thing limiting you. If gaming is on the list at all, skip this band and read the next one.

Around £150 to £350. This is where most gaming builds sit, and where the advice splits.

At the lower end, a Ryzen 5 7500F or an Intel Core i5 14400F will not hold back a mid range graphics card at 1080p or 1440p. Both appear in a lot of our builds for exactly that reason.

Above that, the question is whether you want X3D. A Ryzen 7 7800X3D or 9800X3D carries a much larger cache, which raises frame rates in games specifically and does very little for anything else. If the machine is mainly for playing, that is where the money works hardest. There is also a Ryzen 5 7500X3D if you want the cache at a lower spend.

The rule underneath all of it: work out your graphics card first, then buy the processor that will not limit it. Spending up here and down on the card is the wrong way round.

Around £350 to £550. If you edit video, stream while you play, render, or compile, the calculation changes. These are workloads that scale with core count, and the graphics card cannot take the load off you the way it does in a game.

A Ryzen 7 9700X or an Intel Core Ultra 7 270K gives you the core count without paying for the top tier. If you do both, gaming and creative work on the same machine, a Ryzen 7 9800X3D covers the pair, since the extra cache still helps in games and the eight cores handle everything else.

On overclocking: the K on an Intel chip and the X on a Ryzen mean the multiplier is unlocked. Worth knowing, but modern processors already boost close to their limit on their own, and the gains from doing it manually are small compared to buying a tier up. If you want the headroom, budget for a better cooler at the same time.

£550 and up. If you render, run virtual machines, work with large datasets, or genuinely do several heavy things at once, more cores are the answer and this is where you find them.

A Ryzen 9 9950X or an Intel Core Ultra 9 285K gives you sixteen and twenty-four cores respectively on a standard consumer platform, which for most people is where this ends. If you want gaming performance alongside it, the Ryzen 9 9950X3D combines the core count with the X3D cache.

Beyond that sits AMD Threadripper on the sTR5 socket, which is a different class of machine with different motherboards and memory requirements. It is worth it if you are earning from the work. If you are not, a 9950X is the sensible ceiling.

Both manufacturers use a tier number to tell you roughly where a processor sits. AMD runs Ryzen 3, 5, 7 and 9. Intel now runs Core Ultra 5, 7 and 9, having dropped the older Core i3, i5, i7 and i9 naming when it moved to the Core Ultra Series 2 platform. You will still see Core i5 and i7 on the previous generation, which remains good value.

After the tier comes the generation and the model. On a Ryzen 7 9800X3D, the 9 is the generation and the rest identifies the specific chip. On an Intel Core Ultra 7 265KF, the 2 marks Series 2 and the 65 places it within that series. Higher numbers within a family generally mean more cores, higher clocks or both.

Then come the letters at the end, which are the part most people skip and the part that changes what you can do with the chip. Those are worth knowing before you buy.

Both manufacturers refresh their processor lines every year or two. The current platforms are AMD's AM5 socket, running Ryzen 7000, 8000 and 9000 series, and Intel's LGA1851 socket, running Core Ultra Series 2. The previous Intel platform, LGA1700, covers 12th to 14th generation Core processors and is still widely sold.

Buying a generation behind is often good value, and the performance gap between adjacent generations is usually smaller than the price gap. The thing it costs you is upgrade path. AM5 will take several more processor generations, so a Ryzen 5 bought today can become a Ryzen 9 later on the same board. LGA1700 is at the end of its life, so a 14400F is likely the last processor that board will ever hold.

If you expect to upgrade the processor without rebuilding the machine, that is the deciding factor, not the generation number itself.

A spec sheet gives you a lot of numbers. These are the ones that matter:

• Cores: Separate processors on one chip, each handling its own work. Six is the practical minimum now, eight covers gaming comfortably, and above that you are buying for creative work rather than games. Most current gaming chips sit between six and sixteen.
• Threads: How many independent tasks the chip can handle at once. Multithreading lets one core run two threads, so an eight core chip usually reports sixteen. It matters for editing, rendering and streaming. It does very little in games.
• TDP: Thermal design power, in watts. It tells you how much heat the processor produces, which decides what cooler you need and feeds into your power supply calculation. A 65W chip runs happily on air. A 250W chip needs a serious cooler and the case airflow to support it.
• Cache: Fast memory on the chip itself, holding data the processor is about to need. There are three levels, L1 smallest and fastest through to L3 largest and slowest, and anything not held there has to come from system memory, which is far slower. AMD's X3D chips stack a much larger L3 cache onto the die, and because games repeatedly ask for the same small set of data, holding more of it on the chip raises frame rates noticeably. It does almost nothing for productivity benchmarks, which is why an X3D chip can lead in games while trailing elsewhere.
• Clock Speed: Measured in gigahertz. Higher is faster, but only when comparing chips of the same generation and design. A modern processor at 4.7GHz will beat an older one at 5.2GHz. You will see a base speed and a boost speed listed; the boost figure is what you get most of the time.
• IPC: Instructions per clock. How much work the chip does per cycle, which is why generation matters more than raw clock speed. You will not find it on a spec sheet, but it is the reason newer is faster at the same GHz.

The socket is the physical connection between the processor and the motherboard, and it is the one compatibility check that cannot be worked around. A Ryzen 9000 chip will not fit an AM4 board, and a Core Ultra will not fit an LGA1700 board, regardless of what else the specifications say.

If you already have a motherboard, the socket decides what you can buy. If you are building new, choosing the socket first makes everything after it simpler. Our motherboard bundles pair a processor with a compatible board, so the check is already done.

Three things to decide - What you do with the machine - which sets how many cores you need, whether you play more than you create - which decides whether X3D is worth it, and what socket you are on - which decides what will fit.

For gaming, the processor's job is to not hold the graphics card back. Work out the card first, then buy the processor that clears that bar, and put what is left into memory and storage rather than into a higher tier chip that will not add frames.

Where to go next 

• Gaming PC buying guide for the whole decision, not just the processorer.
• Motherboard buyer guide for chipsets and what each one gives you.
• GPU buyer guide for the component that sets your frame rate

Ready to buy 

• AMD gaming PCs and Ryzen 7 gaming PCs for X3D builds.
• Intel gaming PCs for Core Ultra builds.
• Motherboard bundles if you are building yourself and want the compatibility handled.
• PC configurator to build your machine.