Building your own PC, or upgrading an existing computer? Here’s everything you need to know about the PC components you’ll need for the job.

This article is part of an educational series about PC components. Click here to see the rest of the series.

For many people, buying a new desktop PC is a matter of choosing a favourite manufacturer, and a model targeted at a specific task. However, there are many situations where you’ll want to improve on a good thing with specialized components: a fast video graphics card, for example, can turn an average gaming PC into a gaming powerhouse that delivers a competitive edge to players. Some people prefer to build their own computer, selecting each component as they go. Others will select specific items to upgrade the one they already own so that it operates more efficiently. In each situation, you’ll need information about PC components.

What are the things you need to consider before building your own computer, or upgrading an existing PC?

Table of Contents:

      1. Build your own computer, or upgrade an existing PC
      2. Central processing units (CPUs)
      3. Motherboards
      4. Graphics/video cards or GPU
      5. Memory (DRAM) and storage (internal SSDs and HDDs)
      6. Power Supply (PSU) and cases
      7. CPU fans and cooling
      8. Others

Build your own computer, or upgrade an existing PC

Pc components buying guideThe first step is to know what your goals and budget are.

Assuming you don’t have an unlimited budget, choosing the components is a matter of weighing performance and the biggest bang-for-buck components against your overall build budget. For example, PC gamers may choose to allocate more of their budget to a high-performance graphics card. From there, you start assembling the collection of components, keeping compatibility and those end goals first and foremost. It’s also important to think a bit in the future, planning not just for what you need now, but also thinking about what you might need a year down the road.

Building or upgrading your own computer takes longer than buying one off the shelf, but many people enjoy the experience. And you get complete, granular control of the results, from the performance to the appearance of the computer.

Main PC components for a new build or upgrade

Here are the primary components you’ll need to consider when building your own computer: CPU, graphics card, motherboard, RAM, storage, cooling, case, and power supply. Any one of these components might also be a candidate for an upgrade in an existing machine.

Central processing units (CPUs)

The central processing unit (or CPU) is the brain of the computer.

The CPU is also a PC component that can be upgraded, so long as you stick to an option that is compatible with your motherboard. Why would you want to upgrade the CPU in an existing PC? If general performance is lagging expectations and the CPU is frequently 100% utilized, or an application you want to run requires a more powerful CPU, then an upgrade is an option. Not sure if your CPU is the bottleneck? Windows 10’s Task Manager can show you real-time performance stats. You can also bring your PC to Geek Squad for an evaluation. 

Pc components buying guideThe two brands you need to be aware of when choosing a CPU are Intel and AMD. You’ll usually find the CPU mentioned early in the description of a computer (e.g., “Intel Core i5” or “AMD Ryzen 5”) because of its importance. The CPU does the heavy lifting in terms of the computer’s operation—it executes instructions. That translates into running software, from the operating system to the applications. A more powerful CPU runs more instructions, faster, contributing to a better experience no matter what you use the computer for. Here are some characteristics to consider when purchasing a CPU: Cores and clock speed, cache, and compatibility with the motherboard.

CPUs are equipped with multiple cores. Each core is almost like a mini CPU, able to perform an instruction on its own. The more cores the CPU has, the more instructions that can processed simultaneously. Multi-threading allows each core in turn to perform multiple tasks simultaneously. Cores are hardware, threads are virtual, so more cores trumps multithreading. Most basic desktop PC CPUs today offer four cores. High end gaming PCs can have 16 cores or more.

Clock speed (measured in GHz) measures how fast the CPU operates, basically giving an indication of how many instructions the CPU can perform in a second. Higher GHz is faster, but only when comparing similar CPUs (for example a 3GHz CPU from two years ago is likely slower than a current 2GHz chip). CPUs may be locked—which means they can hit a maximum clock speed. Some are sold unlocked, which means the owner has the option of manually “overclocking” them beyond the base speed.

Unlocked CPUs allow you to manually increase the clock speed through the computer’s BIOS. The BIOS is software that comes with the motherboard, and controls a number of hardware options. It can edited through the BIOS Setup Utility, but users should know what they’re doing before making changes at this level. Manually increasing the clock speed makes the processor faster, but generates additional heat that the standard heat sink and fan weren’t designed for, so you’ll need to plan for supplemental CPU cooling. Overclocking is a process of slowly boosting the clock speed, then testing PC stability until you reach the maximum speed at which your computer runs reliably.

Cache is onboard memory where instructions are temporarily stored for faster performance. L1 cache is the fastest, L2 has more capacity but isn’t quite as fast, while L3 has the highest capacity but the slowest speed. Regardless, all cache memory is faster than RAM.

Generally speaking, clock speed is more important for gaming (snappier performance), while core count is more important for processing (completing more tasks in a shorter time).

Pc components buying guideCompatibility with the motherboard is critical. Make certain that the motherboard’s socket is compatible with the CPU you choose because the CPU will be “plugged in” to the motherboard. AMD and Intel CPUs require different motherboard sockets, and within each there is a range of different socket types depending on CPU generation. Check the documentation of your CPU and the motherboard to be certain because the two must match. Among the latest round of CPUs from AMD and Intel, AMD processors require a motherboard with an AM4 socket, while Intel CPUs require an LGA 1200 socket. Also pay attention to the CPU’s power requirement (measured in watts) to ensure your computer’s power supply is up to the task.


Every component of your computer plugs into the motherboard, so that makes it a critical part of your PC build. There is one very important factor in choosing a motherboard. The one you choose must have a socket that’s compatible with your CPU. The processor and socket on the motherboard (e.g. LGA 1200, which will be displayed on the CPU and processor packaging) must be a direct match. There is no wiggle room here—if they aren’t compatible, the PC is a non-starter.

Pc components buying guide

Motherboards are offered in different standard sizes: ATX (the largest), Mini-ITX (the smallest) and Micro-ATX (in between). Larger motherboards have the space and slots for more components, and more input and output (I/O) ports. Smaller motherboards are used when you want a desktop PC that takes up less physical space. The standard motherboard size—especially with gaming PCs—is ATX, with some more compact gaming/performance PCs using Micro-ATX. 

What you need to think about is how many full-sized x16 PCIe slots (typically used for video cards) you’ll need. Some motherboards are equipped with smaller PCIe slots as well, for components like sound cards. Also important are the number of RAM slots, as well as the speed of RAM supported. What I/O ports will be important to you? USB Type-A (USB 3.0 and 3.1) are used by most wired accessories, while newer ones might support USB Type-C (USB 3.1/3.2 Gen2). If you will be using the CPU’s integrated graphics instead of a video card, you’ll need to pick a motherboard that supports video output like HDMI or DisplayPort. 

Additional slots to be aware of are SATA, IDE and m.2 slots for storage.

Other things to watch for? Some motherboards will have integrated Wi-Fi, but not all do. If the PC will be using a wired network connection, many boards include integrated Gigabit Ethernet. Some include onboard audio. Some (aimed primarily at the PC gaming crowd) also incorporate integrated RGB lighting.

Basically, you need to pick a motherboard that’s compatible with your CPU, and one that has the right combination of expansion slots and connectors to meet your requirements. 

Graphics/video cards or GPU

If your PC is intended for everyday use, you probably won’t need a graphics card. Most desktop CPUs released in the past two years feature integrated graphics (a GPU that’s part of the processor) that are powerful enough to support 4K streaming and video output. 

However, for applications that are graphics-intensive, like gaming, image and video processing, virtual reality, or software that is GPU-accelerated, you will want to install a graphics card (sometimes referred to as a video card). Video cards also support adaptive sync technology (G-SYNC and FreeSync) that improve the appearance of video game graphics when used with a compatible monitor. The companies that make these standalone GPUs are NVIDIA and AMD. They sell their own branded graphics cards, but both also license their GPUs for use in graphics cards from third parties. The latest generation of graphics cards are incredibly powerful, with features such as real-time ray tracing, AI-acceleration, and even 8K video output. 

Pc components buying guide

Graphics cards plug into a PCIe x16 slot on the motherboard. They are fairly self-contained components, with their own integrated cooling fans—video cards generate a lot of heat. There are a wide range of options for graphics cards, with differing generations of GPU architecture, varying numbers of cores, and different amounts and speeds of dedicated video memory (VRAM).

How do you choose the right graphics card for your PC? First, set a budget. There are many affordable options, but the cost increases with performance; at the high end, a flagship graphics card can cost as much as a new PC. 

You’ll want to check your motherboard and any graphics card to make certain the PCIe slot is a match for the connector on the card. You should also verify the slot is actually PCIe x16, and not something else like PCIe x4 that looks the same, but has much lower bandwidth (the slot will be labelled). Some motherboards may require that a graphics card be installed in a specific PCIe slot.

Look for the graphics cards requirements of the games and applications you want to run on the computer. Also pay attention to video outputs offered by the card. Do you want HDMI, Thunderbolt, DisplayPort or other video connection standards? At minimum, you’ll want a video card that satisfies your requirements, but you may want to go a level up for future-proofing.

Make sure your power supply is able to handle the high demand of the graphics card; this will be indicated in watts. And don’t forget to confirm that the graphics card will physically fit within your computer’s case.

Memory (DRAM) and storage (internal SSDs and HDDs)

Now it’s time to consider Gigabytes (GB) and Terabytes (GB). Memory and storage.

RAM (Random Access Memory) is where the computer stores information for rapid access. When a computer doesn’t have sufficient RAM, you’ll know it. The system will slow as you open more windows. Some applications will refuse to launch. The computer can become unstable.

Fortunately, RAM is an easy and affordable upgrade. It’s sold in DRAM sticks and measured in GB. Your PC’s motherboard is equipped with RAM slots.

Pc components buying guideNot all RAM is the same … That would be too easy. Instead there are technical factors to consider. First is generation. The current generation of RAM is DDR4, and the previous generation is DDR3. The standard for DDR5 RAM was recently approved, but it is still rare. Newer generations of RAM are faster, and each generation brings new improvements. For example DDR4 upped the maximum RAM per DRAM stick to 32GB from DDR3’s 16GB. You also need to consider clock speed, with a higher clock speed being faster.

When choosing DRAM for your PC, you need to factor in which generation of RAM your motherboard supports (such as DDR4), the number of slots available, and how much RAM you need for optimal operation. An everyday PC may be able to get away with 8GB of DDR3 RAM, but a gaming PC is more likely to have 16GB or 24GB of DDR4 RAM. When upgrading or installing RAM, it is usually done with matching pairs of DRAM sticks for optimal performance.

Computer storage is one of the most commonly upgraded components. This is where all your software is installed and all your files reside. Desktop PC storage currently comes in three variations.

Pc components buying guideHard drives (HDDs) are the spinning disks that have been in use for decades. They offer affordable storage in very high capacities, including 4TB, 8TB and even 12TB options. Among HDDs, 7200 rpm drives are faster that 5400 rpm models, but they do carry a slight price premium.  

Pc components buying guideSolid state drives (SSDs) ditch the moving parts for the speed of microchips. An SSD is orders of magnitude faster than an HDD at reading and writing data, and this speed also translates into much faster boot times and snappier system performance in general. SSDs have historically been more expensive and available in lower capacity than HDDs, but 1TB internal SSDs are now common.

Pc components buying guideFinally, the latest development in solid state storage is M.2 PCIe SSDs. These look like a DRAM stick, bring further speed gains, but require a motherboard with an M.2 slot for installation. A computer motherboard will have SATA connectors to plug in HDDs and SSDs, which are mounted in brackets in the PC case.

Your PC might use multiple storage options. For example, a popular configuration is modest capacity SSD to install the operating system and a few commonly used applications. High capacity HDDs are used for mass storage. This combination offers the snappy system response of SSDs, with affordable mass storage for libraries of files. 

Power Supply (PSU) and cases

Pc components buying guideThe power supply (or PSU) is obviously an important consideration when building a PC, and it can play a large role in upgrades as well. The power supply provides the power for each and every component. That means the power supply has to meet the continuous and peak power requirement for every component. Big power users include the CPU (remember, power draw will increase if you overclock it), and the GPU. Fortunately there are online calculators that can help figure this out, but 500 watts is a good minimum starting point if there’s a graphics card installed. 

Also watch for power efficiency (80 Plus rating). 80 Plus Bronze is 85% power efficient, Gold is 90%, and the highest is 80 Plus Titanium at 94%. The higher the efficiency, the less electricity is being wasted as heat.

PC builders have a choice between modular, non-modular, and semi-modular PSUs. Modular power supplies allow you to connect or disconnect power cables between the PSU and components. Non-modular PSUs have all the power cables permanently attached. Semi-modular PSU’s are in the middle with some power cables permanently attached and some removable. Why would you care? A modular PSU means only the power cables your PC requires are installed, making for tidier cable management. On the other hand, because it lacks all those plugs, a non-modular power supply takes up less room.

The computer case serves a practical purpose (it holds all the PC components), but it’s also an opportunity to make a statement.

Pc components buying guideComputer cases come in various sizes to accommodate the different sizes of motherboards, and components like graphics cards. Cases also differ in their accessibility. Some have easily removable sides, others require a screwdriver to open up. They will vary in terms of the number of drive bays, the slots for inputs and outputs, and cable management.

Mid-tower ATX cases are probably the most popular for PC builds. They provide the space for an ATX motherboard, a full-sized graphics card and plenty of storage—without taking up the same room as a full-tower case.

Once you get past the basic functionality of the computer case, it’s time to consider personalization options. Cases come in different styles, ranging from minimalist to aggressively sculpted. There are different colour options. Some have clear glass or plexiglass sides so you can show off your PC build. Then there’s RGB lighting. With integrated RGB lighting, a PC case can be completely customized and fit right in to a PC gaming setup. 

CPU fans and cooling

Finally, don’t forget CPU fans and cooling. All of those components generate a lot of heat, and they’re packed inside a closed case. Without effective cooling, components will overheat. That means performance slowdowns, spontaneous system shutdowns, and even the risk of physical damage. 

Pc components buying guide

The primary concern in a PC build will be the CPU. Most CPUs include a basic fan in the box.  That’s intended for everyday use. If you plan to just use the PC for web browsing or streaming video, it should be fine. Anything that pushes the CPU on a regular basis (such as gaming), or if you choose to overclock the CPU, you’ll need to invest in a CPU fan that’s more capable of cooling the CPU and moving out the heat it generates. 

An air cooler is essentially a beefier CPU fan, with a more effective, finned heatsink. Liquid cooling is generally considered to be more effective and quieter than air cooling. These systems circulate a liquid (usually distilled water) past the CPU to pick up heat, then through a radiator where a fan blows away the hot air, with a pump circulating the cool liquid back to the CPU. It basically works like the radiator in a car.

Pc components buying guideYour computer case may or may not have come with cooling fans. These fans draw air in, pass it through the case and then blow it out the back of the PC. This helps to dissipate the heat generated by all the PC components that don’t have their own cooling systems. You need a filtered intake fan, and an exhaust fan—both capable of moving the same amount of air (being out of balance can lead to problems like dust building up in the case).


Pc components buying guideThere are other PC components that might be part of your computer build or upgrade. These might include optical drives, sound cards, video capture cards, network interface cards, and cables. You’ll find all of these components and more at Best Buy.

Operating System

Pc components buying guideOnce your PC is built, you’ll need to install an operating system. Chances are, that’s Windows 10. You’ll find all the varieties, including Windows 10 Home and Windows 10 Pro, at Best Buy.

Next steps

If you’ve decided to build your own ultra high-performance, customized gaming PC, you want to build a PC as a DIY project, or your existing computer would benefit from an upgrade or two, you know that Best Buy has all the computer components you’ll need.

Pc components buying guideThe next step is to do your research. Before choosing a specific component for your build, read the documentation to ensure compatibility. Review the specifications. Read product reviews—don’t forget, you’ll find hands-on reviews and ratings from customers on Best Buy product pages. Compare. Then choose the components that are best-suited to your requirements.

When your PC is ready to go, don’t forget that Best buy also carries all the computer accessories that will ensure you get the most out of your desktop computer experience, including keyboards, mice, monitors, printers, speakers, headphones, webcams, cables, external storage, software, and the latest Wi-Fi routers.  

Best Buy is one of Canada’s largest and most successful retailers, operating the Best Buy (, Best Buy Mobile, and Geek Squad ( brands.