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How to Buy the Right CPU: A Guide for 2021

Choosing the best CPU matters a lot, whether you’re upgrading your existing system or building a new PC. Higher clock speeds and core counts can make a major difference in performance, providing a snappier system, smoother gameplay and faster completion of intensive tasks such as video editing and transcoding. Plus, the CPU you choose will also dictate your motherboard options, as each processor only works with a specific CPU socket and set of chipsets.

Also, like most aspects of consumer tech, you'll have to decide to buy the best processor that's available right now, or wait to see what next-generation chips bring to the table. AMD's Ryzen 5000 CPUs are impressive, finally generally overtaking competing Intel CPUs in single- and multi-core performance. But due to a combination of high demand, limited capacity at TSMC's chip fabs and the ongoing pandemic, AMD's latest CPUs have been very hard to find in stock at or near their MSRPs since launch. 

Meanwhile, Intel is about to finally move away from a Skylake-based architecture, with Rocket Lake-S. Intel's new chips promise solid single-core performance gains of their own, as well as a sift to a platform that finally supports PCI 4.0 -- a feature AMD rolled out in its Ryzen chips nearly two years ago.

(Image credit: Connect world/Shutterstock)

If you already know a lot about CPU specs and want recommendations, check out our picks for best CPUs for gaming and best CPUs for workstations and the best cheap CPUs of 2021, tested and ranked. We also have a list of the best chips on the market according to their CPU Benchmarks. But no matter which desktop processor you get, here are some things to keep in mind.

TLDR:

  • AMD has overtaken Intel (for now): These days, you'll often get more for less with an AMD processor, including a nice in-box cooler (although not with the highest-end Ryzen 7 and 9 Ryzen 5000 models) and more cores/threads. Gaming performance has also shifted in favor of AMD for the most part, with the Ryzen 5 5600X overtaking even higher-end Intel CPUs at 1080p and stock settings. And AMD has long handled tasks like video editing faster. But the 1080p gaming performance edge may shift back to Intel once Rocket Lake-S arrives.
  • For many tasks, clock speed is more important than core count: Higher clock speeds translate to snappier performance in simple, common tasks such as gaming, while more cores will help you get through time-consuming workloads faster.

AMD or Intel: Which Should You Get?

Up until 2017, AMD was the clear underdog. But with its Ryzen / Threadripper series chips, the company has moved steadily toward performance parity with Intel. And with Ryzen 5000 and chips like the Ryzen 5 5600X in particular, AMD has in most respects moved past Intel's current offerings, often delivering better performance in both light and heavy workloads that tax many cores. The matchup may change substantially though, once Intel's latest Rocket Lake-S CPUs arrive later in 2021.

All that said, both companies may very capable CPUs. Some fans will have strong opinions, but if you don't have your heart set on one brand or the other, you should be open to either. For much more on this, see our Intel vs AMD: Who Makes the Best CPUs? feature.

What do you want to do with your CPU?

It's tempting to just spend as much as you can afford for a CPU, but you might be better off saving some of your cash for other components. Determine your processor type and max budget based on what you need your computer to do.

  • Basic tasks: $50-$100 range. If you’re only after a chip that will let you watch video, browse the Web, and do basic productivity tasks like word processing and light spreadsheet work, then an entry-level chip with two or four cores might be just what you need. But if you often find yourself doing more than one of those basic tasks at once, it would be better to step up a model or two. Consider a Ryzen 3, like the AMD Ryzen 3 1300X or AMD Ryzen 3 2200G, or Intel Pentium on the high end of this price range and an Intel Celeron or chips like AMD's Athlon 200GE on the low end.
  • Gaming: $200-$300 range. If you’re primarily interested in high-end gaming performance, you should opt for a mid-range Intel Core i5 or AMD Ryzen 5 CPU with high clock speeds. Considering that the graphics card is more important for gaming than the processor, you can save money by not getting a more powerful Core i7 or Ryzen 7 chip.
  • Creative media work or overclocking: $300-$400 range. If you want more cores or speed for things like video editing—or you just want a fast, capable system with extra overhead for future computing tasks, splurge on a Ryzen 7 chip.
  • Workstation muscle: $400+. If you often find yourself waiting minutes or hours for your current system to render your 3D animation or 4K video, or you’re dealing with massive databases and complex math, consider an Intel Core X or AMD Threadripper CPU. These beasts offer massive amounts of physical cores (up to 64 as of this writing) for extreme multitasking (ex: gaming at high settings while streaming and editing) or time-consuming compute tasks. Business users can consider an Intel Xeon (like the recent Xeon W-3175X) or AMD EPYC processor, but those aren't consumer friendly--or reasonably affordable. For those not quite willing to step up to multi-thousand-dollar CPUs and platforms, AMD's 16-core Ryzen 9 5950X or 12-core Ryzen 9 5900X are both excellent alternatives that basically bring workstation-class performance to a mainstream platform.

What generation CPU do you need?

Intel Core and AMD Ryzen CPUs

Each year or so, Intel and AMD upgrade their processor lines with a new architecture. Intel is about to launch its "11th Gen Core Series," with the Core i9 11900K at the top end. AMD's latest chips are part of its Ryzen 5000 line, like the AMD Ryzen 5 5600X, Ryzen 7 5800X, and Ryzen 9 3900X. When looking at the model number, you can see the generation as the first digit of the four number (ex: the 8 in Core i7-8400 or the 3 in Ryzen 7 5700X). Note, though, that AMD skipped 4000 branding on its desktop CPUs.

How do you read the model names and numbers?

The jumble of brands and numbers that make up a CPU product name can be confusing. Intel and AMD both break down most of their chips into “good, better, best” categories, starting with Core i3/Ryzen 3, stepping up to Core i5/Ryzen 5, Core i7/Ryzen 7, and Core i9/Ryzen 9. Intel has the Core i9-10900K at the top of its mainstream product stack, as well as extreme/premium tier like the Core i9-10980XE, priced at around $1,000, just as AMD has Threadripper. But for the vast majority of users, these chips are unnecessary and well out of most people’s price ranges.

For users on a tight budget, Intel offers its Celeron and Pentium chips (Pentium is slightly faster) while AMD has its Athlon line. On the extreme high-end, you'll find AMD's Threadripper and Intel's Core X series, along with the Core X/i9 and Xeon W (both mentioned above).

Now, what about the model numbers that come after the 3, 5, or 7? The first digit designates the product generation (Intel’s Core i7-8700 is an 8th Generation Core processor, and AMD’s Ryzen 5 2600 is a 2nd Generation Ryzen processor). The rest of the numbers just mark various models in the line, with higher generally being better (with more cores and/or higher clocks), while a “K” at the end of an Intel chip means it’s unlocked for overclocking. Only a handful of mainstream Intel chips are “K” skus, while nearly all of AMD’s Ryzen processors are unlocked for overclocking (no “K” designation required). An X at the end of AMD model numbers means higher stock clock speeds.

Should you overclock?

Overclocking, the practice of pushing a CPU to its limits by getting it to run at higher-than-specced clock speeds, is an artform that many enthusiasts enjoy practicing. But, if you're not in it for the challenge of seeing just how fast you can get your chip to go without crashing, overclocking may not be worth the time or money for the average user.

In order to make your CPU achieve significantly higher clock speeds than it is rated for out of the box, you'll likely spend extra on an enhanced cooling system and an overclocking-friendly motherboard. While nearly all recent AMD chips are overclockable to some extent, if you want to dial up an Intel chip, you'll have to pay extra for one of its K-series processors (which don't come with coolers). By the time you factor in all these extra costs, if you're not shopping near the top of the CPU stack already, you'd be better off budgeting another $50-$100 (£30-£70) for a CPU that comes with higher clock speeds out of the box. And remember, even if you do get all the right equipment, you could still get a chip that doesn't overclock well. Or worse if you don't know what you're doing, you could damage your CPU or shorten its lifespan by pushing too much voltage through it.

What are the key CPU specs and which should I care about?

If you're looking at a spec sheet for a given CPU, you'll see a lot of numbers. Here's what to look out for.

  • Clock speeds: Measured in gigahertz (GHz), this is the speed at which the chip operates, so higher is faster. Most modern CPUs adjust their clock speeds up or down based on the task and their temperature, so you'll see a base (minimum) clock speed and a turbo (maximum) speed listed.
  • Cores: These are the processors within the processor. Modern CPUs have between two and 64 cores, with most processors containing four to eight. Each one is capable of handling its own tasks. In most cases these days, you'll want at least four cores--or at least four threads (see below).
  • Threads: This is the number of independent processes a chip can handle at once, which in theory would be the same as the number of cores. However, many processors have multithreading capability, which allows a single core to create two threads. Intel calls this Hyper-Threading and AMD calls it SMT (Simultaneous Multithreading). More threads means better multitasking and enhanced performance on heavily-threaded apps such as video editors and transcoders.
  • TDP: The Thermal Design Profile/Power (TDP) is the maximum amount of heat that a chip generates (or should generate) at stock speeds, as measured in watts. By knowing that--for example--the Intel Core i7-8700K has a TDP of 95 watts, you can make sure you have a CPU cooler that can handle that amount of heat dissipation and also that your PSU can provide enough juice. But note that CPUs put out significantly more heat when overclocked. It's good to know what your TDP is so you can get the right cooling and power equipment to support your CPU. Also, a higher TDP usually coincides with faster performance, although things like process node size and general architecture efficiency come into play there as well.
  • Cache: processor's on-board cache is used to speed up access to data and instructions between your CPU and RAM. There are three types of cache: L1 is the fastest, but cramped, L2 is roomier but slower, and L3 is spacious, but comparatively sluggish. When the data a CPU needs isn’t available in any of these places, it reaches for the RAM, which is much slower--in part because it's physically farther away than a CPU's on-chip cache.

You shouldn't pay too much attention to cache size, because it's hard to equate to real-world performance, and there are more important factors to consider.

  • IPC: Even if you have two CPUs that have the same clock speed and number of threads, if they’re from different companies, or built on different architectures from the same company, they will will deliver different levels of IPC (instructions per clock cycle). IPC is heavily dependent on the CPU's architecture, so chips from newer generations (ex: a Ryzen 5 5600X with Zen 3versus a Ryzen 7 2700X with Zen+) will be better than older ones.

IPC is not usually listed as a spec and is usually measured through benchmark testing, so the best way to learn about it is to read our CPU reviews.

What do you need more: clock speed, cores or threads?

The answer to this question really depends on your regular computing tasks. Higher clocks translate to quicker responsiveness and program load times (though RAM and storage speed is key here as well). Higher clock speeds also mean single-threaded tasks (like audio editing and certain older applications) can happen faster. Many popular games are still lightly threaded.

But many modern programs can take advantage of lots of cores and threads. If you do lots of multitasking or edit high-res videos, or do other complex, time-consuming CPU-heavy tasks, you should prioritize the number of cores. But for the vast majority of gamers and general-purpose computer users, a clock speed ranging from 3-4GHz with four to eight cores is plenty.

What socket does my motherboard need for this CPU?

A motherboard socket for a CPU.

Different processors require different socket types. If you already own a motherboard and don't want to replace it, you'll need to purchase a CPU that matches your board's socket. Alternatively, you need to make sure that the motherboard you buy is compatible with your new processor.

For help choosing a motherboard, see our 2021 motherboard buying guide.

With its current-generation Ryzen and Athlon parts (barring Threadripper), AMD has adopted a single socket—AM4. That means you should, with a BIOS update, be able to put a current-generation Ryzen chip into prvious-generation Ryzen motherboard, and vice versa. But due to limitations to the size of available data stored inside BIOS chips and the vast numbers of CPUs AMD has released on AM4, this issue has gotten much more complicated lately.

Intel, on the other hand, has a tendency in recent years not to support backward compatibility with its new chips and older motherboards, even if the socket is effectively the same. For instance, Intel’s socket LGA 1150 and 1151 differ by a single pin, and the version of 1551 designed specifically for 8th Generation Core chips is physically the same as that made for previous 6th and 7th Generation Core processors. But those older 1151-socket motherboards don’t work with newer 1151-socket CPUs, because (Intel says) the newer chips (which have more cores) have different power delivery subsystem needs. Note that Intel has bucked this trend with socket LGA 1200, which will accept both 10th Gen Intel and upcoming 11th Gen intel CPUs.

Here's a list of all the recent mainstream sockets and their respective chipsets for reference.

Socket and Chipset Table

Intel MainstreamIntel MainstreamAMD MainstreamIntel HEDTAMD HEDT (Threadripper)
Current CPU SocketsLGA 1200LGA 1151AM4LGA 2066TR4
Compatible ChipsetsZ490/Z590, H470/H570, B460/B560, H410/H510Z390, Z370, Z370, Q370, H370, B365, B360, H310X570, X470, X370, B550, B450, B350, B450, A320, X300, A300X299X399

Bottom Line

When choosing a CPU, first ask what you're going to do with it, then see how much you can budget for it after you've figured out how much you're spending on other components. Check our Best SSDs, Best RAMBest Graphics Cards and Best Power Supplies guides for more details. While processors are important, there's no point in pairing a high-speed chip with weak graphics (unless you aren’t a gamer) or a slow, spinning mechanical hard drive. While reading about specs like clock speed and thread count is helpful, the best measure of a processor's performance comes from objective reviews, like those we write here on Tom's Hardware.

MORE: CPU Benchmarks Hierarchy

MORE: All CPU Reviews

MORE: How to Choose a Motherboard

MORE: How to Sell Your Used PC Components

Matt Safford
Matt began piling up computer experience as a child with his Mattel Aquarius. He built his first PC in the late 1990s and ventured into mild PC modding in the early 2000s. He’s spent the last decade covering emerging technology for Smithsonian, Popular Science, and Consumer Reports, while testing components and PCs for Computer Shopper and Digital Trends. When not writing about tech, he’s often walking—through the streets of New York, over the sheep-dotted hills of Scotland, or just at his treadmill desk at home in front of the 50-inch 4K HDR TV that serves as his PC monitor.
  • abryant
    Archived comments are found here: http://www.tomshardware.com/forum/id-3716216/buy-cpu.html
    Reply
  • InvalidError
    21744103 said:
    Intel, on the other hand, has a tendency in recent years not to support backward compatibility with its new chips and older motherboards, even if the socket is effectively the same.
    Recent years? The 8086 used a different package from the 80286 which had a different package from the 80386, which itself used a different package form the 80486, Pentium, Pentium Pro, Pentium II, Pentium III, P4, etc. Intel's history of requiring new motherboards roughly every other year goes back pretty much all the way to its first consumer processor.

    The only thing new "in recent year" is the questionable justifications for forcing people to get new boards since there is nothing new IO-wise to justify it.
    Reply
  • techgeek
    In your chart of Compatible Chipsets, you missed Z390 for LGA1151v2 sockets.
    Reply
  • KenZen2B
    When do you foresee PCIe 4 and PCIe 5 in motherboards ?

    How will the new standards affect gamers or are the new standards for production workloads ?
    Reply
  • InvalidError
    21744970 said:
    When do you foresee PCIe 4 and PCIe 5 in motherboards ?

    How will the new standards affect gamers or are the new standards for production workloads ?
    For AMD, PCIe 4.0 is going to be this summer with Zen 2. For most workloads though, it won't make any difference since there are almost no PCIe 4.0 devices out there, GPUs still don't come close to maxing out 3.0x16 or 4.0x8 yet and the benefits of NVMe over SATA 6G are borderline negligible for most uses, which means even smaller gains from going from 3.0x4 to 4.0x4 or 5.0x4.

    PCIe 4.0/5.0 will have the greatest impact in large servers with massive IO requirements that cannot be met with PCIe 3.0x88 for Intel's Xeon 2S or 3.0x128 for EPYC 2S.
    Reply
  • harly2
    Ryzen, just end it their and look again in 2021 when Intel has something interesting.
    Reply
  • alexander.w.jacob
    In the list of compatible chipsets for the LGA 1151 Z370 is listed twice. I guess one of them should be changed to Z370.
    Reply
  • mitch074
    21744470 said:
    Recent years? The 8086 used a different package from the 80286 which had a different package from the 80386, which itself used a different package form the 80486, Pentium, Pentium Pro, Pentium II, Pentium III, P4, etc. Intel's history of requiring new motherboards roughly every other year goes back pretty much all the way to its first consumer processor.

    The only thing new "in recent year" is the questionable justifications for forcing people to get new boards since there is nothing new IO-wise to justify it.

    At least for these older chips, the fact that the 286 had a different RAM addressing scheme did justify a different pinout - same for the 386DX. But at least, for a time, Intel did provide "Overdrive" processors that allowed someone to plug a 486 in a 386DX system (both CPUs had the same bus width and memory addressing capabilities), or a Pentium in a 486 system (but it was a failure due to the bus being cut in half).

    Let's not mention the days of the Socket 5/7 where a single socket could manage any chip from an original Pentium 75 to a Pentium MMX 233 and also an AMD K6-133 to the K6-3 600 and even Cyrix 6x86 chips... Now THAT was compatibility! But then Intel decided to copyright a CPU's pinout design.

    Let's be honest : Intel didn't want to spend any money into making sure the 1151 design was durable; they reserved a bunch of pins and called it a day, and then only added stuff when needed. If that foced people to buy new motherboards (with an Intel chipset on it), that's only that much cash they get, since they make their own chipset.

    AMD has a different profile : they don't make their own chipsets. As such, they drew up a single socket layout and paid a company (ASmedia) to design a chipset that would work for all that time. And then, they cooked as much back and forward compatibility stuff as they could in the CPU itself
    Reply
  • mspencerl87
    How to buy it??
    Just buy it!
    Reply
  • g-unit1111
    I'm really surprised that the R5-2600 didn't get the Best Value award. It's a 2nd gen hex core Ryzen and it can be had for about $149 which is $50 less than the Intel i5-8400. I just bought one a few weeks ago and it's been a really great buy so far.I bought it with an Asus ROG B450 at Micro Center and for the entire thing I paid $299.You can't beat that.
    Reply