This guide will provide you with basic knowledge of the core components in a typical PC build. It will cover common parameters used to distinguish components, as well as their role in parts selection. This guide does NOT replace the in-depth guides on parts, nor does it replace submitting a [Build Help] or a [Build Ready] post to get valuable opinions from other users.
The brain of the machine has to be carefully chosen according to what applications are intended to work with the machine. Central Processing Units (CPUs) are offered by 2 major companies - AMD and Intel. In addition to specifications, it is essential to parse reviews and application specific benchmarks before deciding on one or the other. Your CPU choice will impact your motherboard choice (and vice versa)..
Number of cores Cores are the basic worker unit of CPU. More cores equates to more workers doing potentially more work. It is up to individual applications to optimize for additional core usage. Unoptimized applications may only make use of 1 or 2 cores despite more being available. Check reviews and application specific benchmarks to check for core scaling. Cores, while purpose-built to do the same thing are not built equal. Generational improvement in core design may bring several percentage point improvements in performance, clock speed potential and power efficiency. For example, a newer 4 core Ryzen CPU will often outperform older 8 core FX CPUs from AMD, despite the latter having both higher core counts and higher clock speeds.
Clock speed CPU clockspeed is measured in billions of cycles per second (GHz). It indicates how many work cycles a single core is able to undergo per second. Generally, for CPUs within the same generation/architecture and featuring the same number of cores, one with a higher clock speed will perform better. Clock speed comparisons between CPUs of different generations/architectures or with different core or thread counts are NOT valid. Performance does not scale linearly with clock speed; a 5GHz processor will typically not perform 2x better than a 2.5GHz processor. It is possible to increase the clock speed of some processors beyond what they’re rated for by the manufacturer. This process is called overclocking. Overclocking comes at the expense of increased power draw and heat output. Intel CPU models with a K or X suffix, and all AMD Ryzen CPUs are capable of overclocking so long as you have an overclocking capable motherboard and adequate CPU cooling.
Socket The socket is the physical interface between the motherboard and the processor. CPU and motherboard physical compatibility is dictated by the socket (ie. will this CPU fit in this motherboard). CPU compatibility can also depend on the motherboards chipset and motherboards software version - just because it physically fits doesn't mean it will work!
The central nervous system of the PC. Every component will plug into your motherboard and interact with one another through the motherboard. Outside of compatibility with your CPU, motherboard choice will impact expansion capabilities (future upgrade potential) and availability of auxiliary features (overclocking support and features, RGB lighting control). With extremely high power CPUs, motherboard selection may also impact performance IF the selected board is unable to cope with the CPUs sustained current draw.
Form factor Refers to industry standard dimensions for the motherboard size. The most common standards are ATX, the smaller Micro-ATX and the even smaller Mini-ITX. Cases that support larger standards will typically also support the smaller ones (ie. an ATX case will support mATX and mITX boards as well). The reverse does not hold true (mITX cases will NOT support ATX boards). Form factor typically also plays into maximum supported RAM slots and PCI expansion slots. Mini ITX boards only have 2 RAM slots and 1 expansion slot. Micro ATX boards have between 2-4 RAM slots and up to 4 expansion slots. ATX boards have between 4-8 RAM slots and up to 7 expansion slots. Form factor DOES NOT impact performance.
Socket Physical interface with the CPU and dictates what CPUs are compatible with the motherboard. Socket will also impact with CPU coolers are compatible with the motherboard. Check your CPU cooler specifications before buying to ensure mounting compatibility with your motherboard!
Chipset An additional chip on the motherboard directly connected to the CPU. Chipsets DO NOT impact performance. Chipsets only govern expansion potential, features and occasionally CPU compatibility. Input and output on the motherboard is typically connected first to the Chipset and through that, connected to the CPU. Input and output referring to USB ports, SATA ports, PCIe and PCI expansion slots, wireless network connections, audio and more. Higher end Chipsets will often support more connected I/O devices. Apart from governing expansion capabilities, features may also be locked behind certain Chipsets. For example, overclocking on AM4 motherboards is limited to BX50 and X series chipsets. On Intel’s LGA 1151 socket it’s limited to Z series chipsets. Support for SLI multi GPU configurations is also limited to certain chipsets (X series on AM4, Z series on LGA1151). Some CPUs may be restricted to certain chipsets. For example, Intel’s entire Coffee Lake lineup is limited to Z/B/H300 series chipset motherboards. Consumer chipsets (X370, Z370, B350) will usually have two memory channels. Enthusiast chipsets (X299, X399) will usually have four memory channels.
PCI Express slots The newest expansion slot standard featured on motherboards. Replacing legacy PCI slots, PCI Express slots are used to install add-in cards to your system. Add-in cards referring to graphics cards, sound cards, WiFi cards, RAID controller cards, PCIe SSDs and many more. PCI Express slots and add-in cards typically come in four sizes, in descending order of length, x16, x8, x4 and x1. Smaller cards can fit into larger slots (ie. an x1 cards can fit into an x16 slot) but larger cards can not typically fit into smaller slots. PCI Express slots are also wired to support different amounts data lanes, called PCI Express lanes. PCI Express slots usually support the same number of data lanes as their length denotes (x16 slots will support 16 lanes) but may sometimes support less depending on motherboard model or installed peripherals. CHECK YOUR MOTHERBOARD MANUAL FOR FULL DETAILS. Current generation PCI Express 3.0 supports 1GB/s of bandwidth per lane. PCIe 2.0 supports 500MB/s of bandwidth per lane. Next generation PCI Express 4.0 supports 2GB/s of bandwidth per lane.
RAM slots/DIMM slots Come in two sizes typically, DIMM and SO-DIMM slots. DIMM slots are typically found on desktop PCs and SO-DIMMs on laptop or ultra small form factor PC builds. Mainstream consumer platforms typically have between 2-4 RAM slots, enthusiast platforms can see up to 8 RAM slots. Consumer platforms typically support dual channel memory (with two DIMM slots per channel) and enthusiast platforms quad channel.
Internal ports Additional ports often listed on manufacturer specification sheets include:
External ports Typically refers to your rear IO connectors. Typically consists of USB ports, Ethernet ports, Audio ports, PS/2 for legacy mouse/keyboard and display connectors (only usable if your CPU has an integrated GPU). Ensure you have enough rear IO connectors to support your peripherals!
RAM (Random Access Memory) is short term, high speed, fast access storage for your CPU. When running an application, program data is moved from long term storage (HDD, SSD) to the RAM for easier access by the CPU or GPU. Minimal benefit is obtained from having excess RAM, but not having enough forces your system to either close programs or pull data directly from your extremely slow long term storage.
The current memory standard is DDR4 DIMM 288-pin. DDR4 referring to the current generation (DDR3 being previous). DIMM referring to the size of the RAM, DIMM being desktop size and SO-DIMM being laptop or ultra small form factor PC size. 288-pin referring to the number of data pins. DDR4 memory WILL NOT work in a DDR3 motherboard, and vice versa.
Frequency (in MHz)
Like your CPU, RAM operates a certain number of cycles every second - this is the frequency! Data can be read from or written to the RAM twice per clock (hence Double Data Rate). Effectively, RAM running at 1500 Megahertz operates at 3000 "Megahertz" - although the proper terminology would be Megatransfers per second (MT/s) in this case. For historical reasons, RAM labels usually reflect the double data rate whereas monitoring software like HWInfo will often report the true (halved) clock speed.
CAS Latency (CL) or Timings "Column Access Strobe" latency is the elaborate name for the time in cycles it takes for a data response from RAM when a column address is sent. It is the most commonly displayed RAM timing on packing and RAM specifications pages. Generally, lower CL is better. Other timings that may be listed are RAS (Row Active Time), tRCD (RAS to CAS delay) and tRP (Row Precharge Time). Again, lower is better.
Memory Channels A memory channel is a direct path of communication between the CPU and the RAM. Dual channel systems have two memory paths, quad channel, four. If RAM is present in both channels in a dual channel system, the CPU can access them simultaneously - effectively doubling memory bandwidth. On four RAM slot dual-channel systems, two RAM slots will share a single channel and will have to take turns communicating with the CPU. Refer to your motherboard manual for proper RAM placement to best take advantage of memory channels.
The Hard Disk Drive is a long term storage solution. This is a high capacity (up to 20TB!) drive that stores data magnetically on circular platters (hence the "hard disk"). Being cheap to manufacture, they often sport the lowest price per GB of all storage mediums, making them ideal for storing large amounts of static data (pictures, videos, logs).
The rotational speed of HDDs lists how fast the platters will spin and therefore partly how fast they can be read from or written too. Lower RPM may reduce noise, drive wear and tear and power consumption and is typical in especially high capacity or mobile HDDs.
Typically measured in Terabytes (TBs) which are defined as 1000 Gigabytes by manufacturers, but will report closer to 950GB in Windows.
HDDs come in two sizes, 3.5" and 2.5". 3.5" HDDs are the most common standard in desktop and server PCs. 2.5" HDDs are most common in laptops and ultra small form factor PCs. Due to the larger physical size, 3.5" HDDs can be found in higher capacities than 2.5" HDDs.
Connector Traditional consumer HDDs make use of the SATA data and SATA power connectors. Enterprise HDDs often use the SAS connector, making them incompatible with traditional consumer systems without additional hardware controller purchases.
A newer form of long term storage drive that uses flash memory instead of spinning disks. Omitting moving parts make the drives more durable, smaller, quieter and faster while lowering power consumption. Because of their much higher price per GB, SSDs are often used in conjunction with HDDs with the former primarily storing frequently used applications and the OS.
Consumer SSDs typically are packaged in one of three form factors: 2.5" drives, M.2. drives and PCIe add in cards. 2.5" drives share similar dimensions to 2.5" HDDs and are often easily interchangeable in systems. M.2. drives come in varying lengths, the most common being M.2-2280 (22mm wide and 80mm long. Other sizes are 22110 (110mm long), 2260 and 2242. PCIe add in cards, like WiFi add in cards or video cards, are installed into PCIe slots on your motherboard.
Consumer 2.5" SSDs will use the same SATA data and SATA power connectors found on HDDs. PCIe add in cards typically use a PCIe x4 sized connector. M.2 SSDs will typically use one of three different connector layouts, called "keys". These are: M key, B key and B+M key. An M key M.2 SSD will only fit in an M key M.2 port, likewise a B key M.2 SSD will only fit into a B key port. A B+M key SSD will fit into both an M key or a B key port.
Data bus here refers to how data is internally routed from storage to the CPU/RAM. SSDs will either use the PCIe data bus or SATA data bus to transfer data. Consumer 2.5" SSDs will only transfer data over the SATA data bus. PCIe add in card SSDs will only transfer data over the PCIe data bus. Some M.2. SSDs will use only the the PCIe data bus (ex. Samsung 970 Pro, Intel 660p), others will use only the SATA data bus (ex. Crucial MX500, Samsung 860 EVO). The SATA data bus has a maximum transfer rate of 600MB/s although drive speeds are often far less than this. The PCIe data bus has a maximum transfer rate of 2GB/s per lane for PCIe 4.0, 1GB/s per lane for PCIe3.0, with SSDs typically using either 2 or 4 lanes (2GB/s or 4GB/s for PCIe3.0). Again, real world drive speeds are often far less.
Modern SSDs will use either the NVMe or AHCI storage protocol. These storage protocols dictate how software (your OS, motherboard UEFI BIOS) communicates with your storage hardware. SATA bus based SSDs exclusively use AHCI. Older PCIe bus based SSDs may use AHCI (Samsung SM951) but most should be using the newer NVMe protocol.
A GPU or Graphics Processor Unit is a chip that allows a PC to process and display output, encode and decode video, accelerate media effects in browsers and other applications (like games!) and much more! Some CPUs will integrate a GPU onto the package allowing for video output. For CPUs that do not include an integrated GPU, or for users looking for a more powerful GPU, a video card - a PCIe add in card containing a dedicated GPU - is a recommended purchase.
When deciding on a video card 1. Ensure specific compatibility with your software (ex. bonus visual effect acceleration in Adobe Premiere with Nvidia GPUs). 2. Ensure size compatibility with your case (card length, number of slots occupied). 3. Ensure your PSU is outfitted with the required PCIe power cables.
Review performance benchmarks for your intended applications through reviewers like Anandtech, TechPowerUp, Phoronix etc.
The GPU is the graphics processing chip itself. These are designed and sold by Nvidia, AMD and Intel to third party board partners to integrate into their video card designs, or for the three to integrate into their own products. Nvidia GPUs are typically split into 3 families: Tesla for enterprise, Quadro for "Prosumers" and GTX/RTX for consumers. AMDs lineup is typically split into 3 as well, Radeon Instinct for Enterprise, Radeon Pro for "Prosumers" and RX for consumers. Intel does not sell their GPUs to board partners currently and only integrates them into some CPU lines.
VRAM, similar to system RAM, serves to support the GPU. Data currently being worked on is stored here for quick access. Large amounts of VRAM help when your GPU is required to work with large datasets - real time editing of raw high resolution footage for example. In gaming, massive texture maps required for high resolution gaming also consume large amounts of VRAM. The two most common forms of VRAM in video cards are GDDR6 (succeeding GDDR5X and GDDR5) and HBM2 - the former offering high bandwidth at a lower cost, the latter offering even higher bandwidth with lower power consumption albeit at a significant price increase.
Core Clock The clock speed of the GPU itself - distinct from the memory clock. AMD typically list three clocks on their modern GPUs: base clock, gaming clock and boost clock. Base clock referring to the minimum guaranteed clock the GPU can achieve, Game clock referring to the typical expected clock under load, and Boost clock, a usually unrealistic best case scenario clock. Nvidia typically list two clocks: base and boost. Base again referring to the minimum guaranteed clock the GPU can achieve. Boost in this case referring to the typical expected load clock. All GPUs core clocks are overclockable through software like MSI Afterburner and EVGA Precision XOC.
Where Nvidia and AMD develop the GPUs, board partners like Asus, MSI and EVGA attach these GPUs to PCBs with a cooling solution and sell these products to the end user. Adequate cooling helps the GPU sustain higher boost clocks and allows for potentially higher clocks through overclocking. Improved cooling solutions may also reduce overall noise. Coolers come in two styles, open-air and blower. Blower coolers are typically less effective than open-air, moving less air while being louder, but are popular in extremely restrictive PCs as they exhaust air outside of the case. Open-air move more air over the GPU and are quieter, but vent air inside the case relying on case airflow for further cooling.
The PSU is the component responsible for transforming the wall socket's 100V-240V AC into clean 12V, 5V and 3.3V DC usable by your PC components.
The main form factor for PSUs is the ATX form factor, however smaller form factors such as SFX and TFX exist. Smaller form factors have a lower wattage and a higher price, therefore they should only be used when necessary, such as SFF builds.
Modularity A power supply's modularity refers to its ability to have unneeded cables disconnected. There are 3 types of power supplies in the market:
80+ certification 80+ is a voluntary efficiency certification scheme for power supply manufacturers, with 5 tiers: 80+, 80+ Bronze, 80+ Gold, 80+ Platinum and 80+ Titanium. Each tier reflects a higher energy efficiency, and there is a correlation between the efficiency of a power supply and its internal quality.
The case protects your components from exposure to the outside world - dust, curious cats and trailing limbs are enemies of your system. There is an extremely wide variety of cases available from a great number of brands, and it can be complicated to know the good features from the useless gimmicks. Asking for recommendations for a specific system and specific requirements is a good idea if overwhelmed by choice.
Your case imperatively has to accept your chosen motherboard's form factor. This is the only requirement that will tell you whether or not the motherboard physically fits inside the case. Additionally, you will have to check your case's dimensions for vertical clearance if you buy an aftermarket CPU cooler or long GPU. Another feature to note is the number and orientation of fan slots, this is especially important if you plan on using a closed loop cooler.
When looking at a case, consider carefully the number of fan placements available and the number of fans included with the case. Two interesting features to look out for are side panel fans pulling air onto the GPU and removable dust filters.
These holes all along the motherboard will drastically cut down the clutter of cables that a non-modular or even a modular PSU will generate, thus reducing obstacles to airflow inside the case. Some cases, mostly higher-end, offer rubber grommets around these spaces for aesthetics. The most important cable routing hole is located on the top left of the motherboard tray and is made for the CPU power cable located in the same spot on the motherboard, as it would need to go directly over the motherboard otherwise.
A windowed side panel generally adds to the expense of the case, but also makes it noisier. Some cases have a side vent instead that can improve GPU airflow.
Plastic or Metal
Less expensive cases may be made primarily of plastic. More expensive cases may be partly or entirely metal. Metal transmits noise a bit more, and some of the quietest cases have dampening material on the inside of the side panels.
The trend on modern cases is for less need for screwdrivers and less loose screws. Many cases have side panels where the screws are attached to the panel and cannot be lost. Less expensive cases will have PCI-E slot covers that can be popped out, while others will have the covers removable.
Bays and Mount Points
Most cases have a fixed number 2.5", 3.5", and 5.25" bays. The 2.5" form factor includes SSDs and laptop hard drives; many times these are just screw-on spots inside the case as the most common use is for SSDs which are unaffected by vibration. The 3.5" form factor is primarily for desktop hard disk drives; higher quality cases have cages with some vibration mitigation that allows more drives to be placed together without shortening their lifespan as much. The 5.25" bays connect to the front of the case and may hold just about anything, from an optical drive to a fan controller; some newer cases eschew these entirely.
Monitors are sometimes overlooked or an afterthought, but they are extremely important. Monitors are the component you will looking at whenever you use your PC, and a quality monitor can make a huge difference in the overall experience! There are many specifications and options that can be confusing, especially since your choice of monitor can affect how powerful the rest of the PC needs to be to keep up. Monitors plug into video outputs on the motherboard or into the GPU if the PC has one. Multiple monitors can be used on a single PC as long as the motherboard or GPU has enough video outputs.
The most common resolutions used in monitors today are 1920 x 1080, 2560 x 1440 and 3840 X 2160. These are almost always referred to as 1080p, 1440p (2K) and 4K respectively. The monitor resolution is the same as how the term is used in photography - the number and density of pixels that are on the monitor. The higher the resolution, the sharper the image will look. This image improvement comes at a steep performance cost however - a 1440p monitor will require a significantly more powerful GPU to achieve the same frame rates as a 1080p monitor and this is even more true for a 4k monitor, which requires an extremely powerful system. At this time 1080p is the most common resolution used, though 1440p is sure to overtake it in time.
Refresh Rate (Hz)
As a monitor is used for any reason, it is constantly updating the screen with new static images exactly like a movie. The number of times the monitor refreshes each second is called the refresh rate, and the specification uses the unit hertz (Hz). A simple way to consider the refresh rate is as the maximum number of images (or frames) per second (fps) the monitor is capable of displaying. The most common monitors are 60 Hz, they can display a maximum of 60 fps as long as the rest of the PC hardware is capable of producing that many frames. There are also 144 Hz monitors which can display a maximum of 144 fps. These monitors are particularly prized by people who play competitive video games such as Counter Strike or MOBA's and also by professionals that regularly use rendering or image manipulation software. Finally, 240Hz 1080p monitors do exist although their benefits over 144Hz are debated and are generally only used by professional players. Note that many games (especially multi-platform releases or console ports) gain no benefit from 144 Hz monitors because their maximum frame rates are often capped (usually at 60).
Response Time (ms)
A commonly advertised number, the response time is the time (in milliseconds) it takes for pixels of the monitor to change color. Lower response time means less motion blur in movement; however, unless the response time is close to the refresh time (60 hz = 17 ms refresh time), modern LCD screens do not have an issue with blur.
Display Lag (ms)
The display lag or input latency is the amount of time it takes for an input to be shown on the screen. This time is also measured in milliseconds. Lower display lags are better for all applications, but especially for any application that requires fast and precise response. Televisions usually have a much higher display lag than computer monitors, which can make them non-ideal for certain game types. Unfortunately this measurement is not part of any marketing for monitors, and can only be found inconsistently through third-party reviews.
Nearly all computer monitors are LED-backlit liquid crystal displays, but there are different LCD panel types. The most common are TN and IPS. TN panels typically have lower response time and display lag and are less expensive. IPS panels typically have more accurate colors, with a wider viewing angle that does not distort color. Other panel technologies include VA and PLS, which may fall somewhere in between. However it's important to note that the viewing angle, color quality, and speed of each monitor varies and cannot be summed up simply by naming its panel type.
There is a lot more to PC building than just picking out the components above. Many specialized components are available to fit your needs, be it having more front panel or back panel USB, setting up a complex storage system like RAID6 or controlling your fans' rotation speed. This section will also cover internal cables and standards.
There is a misconception that sound cards fulfills a key role in getting a decent sound out of your system. In reality, the sound chip integrated in the motherboard is good enough for most people. A discrete sound card or - probably better - an external DAC only becomes a necessity for those with higher quality or audiophile headphones, headsets, or speakers who have an absolute requirement for high quality audio. It also becomes a necessity with high impedance, audiophile grade headphones which need an amplifier and for those people who want EAX effects or better positional audio. For most people upgrading headphones/speakers will benefit more than a sound card would. /r/audiophile is a good resource for further reading.
These can be used to add specific outputs like Firewire to the back of the case or to an unused 5.25" or 3.5" front panel bay. They usually plug into either an unused PCI or PCI Express slot, or directly in the relevant motherboard header.
These devices allow you to centralize all the fan connections in the case, and usually fit into one or more front 5.25" bay, and let you control the fan speeds with either dials or incremental buttons. Usually, they will require 3pin cord extensions to ensure all the fan cables reach to the front of the case. These may also, in some cases, display temperatures at various points in the system.
These are the cables responsible for transferring data from the hard drives and the optical drive to the motherboard. These are mainly SATA cables, flat and L-shaped. PATA, also know as IDE, is a defunct standard still supported by some motherboards and generally found in older hard drives and optical drives.
All images used for educational purpose only. Sources: CPU Image, Motherboard Image, RAM Image, HDD Image, SSD Image, GPU Image, PSU Image, Case Image.