A motherboard is the main circuit board inside a computer that connects every other component and lets them communicate. It holds the processor, memory, and storage, provides slots for expansion cards, and distributes power and data throughout the system. The motherboard's socket, chipset, and form factor decide which parts a computer supports and how much it can be upgraded.
Motherboard Essentials at a Glance
The motherboard connects the processor, memory, storage, graphics, and ports
The central processing unit (CPU) socket determines which processors fit
The chipset controls features like the number of USB ports, storage drives, and Peripheral Component Interconnect Express (PCIe) lanes
Form factors such as ATX, microATX, and Mini-ITX set the board's size and number of slots
Firmware stored on the motherboard starts the computer and manages hardware settings
Parts of a Motherboard
Part | What it does |
CPU socket | Holds the processor and connects it to the board |
Chipset | Manages communication between the processor and other components, such as storage and USB |
Memory slots | Hold RAM modules, usually 2 or 4 in desktops |
M.2 slots | Hold compact SSDs directly on the board |
PCIe expansion slots | Accept graphics cards, network cards, and other add-in cards |
Serial ATA (SATA) ports | Connect 2.5-inch and 3.5-inch drives with cables |
Power connectors | Receive power from the power supply for the board and processor |
Voltage regulator modules (VRMs) | Deliver steady, clean power to the processor |
Firmware chip | Stores the BIOS or UEFI firmware that starts the computer |
Rear I/O panel | Provides USB, network, audio, and display ports on the back of the computer |
Front panel headers | Connect the case's power button, front USB ports, and audio jacks |
Not every board has every part. Compact and laptop motherboards often skip expansion slots and build components directly onto the board.
CPU Sockets
The CPU socket is the connector that holds the processor. Each socket fits only processors designed for it, so the socket is the first thing to check when choosing or upgrading a desktop processor.
Land grid array (LGA): The pins are in the socket, and the processor has flat contacts. Intel desktop processors and recent AMD desktop processors use LGA sockets.
Pin grid array (PGA): The pins are on the processor and fit into holes in the socket. Many older AMD desktop processors used PGA.
Ball grid array (BGA): The processor is soldered directly to the board. Most laptops use BGA, which is why their processors can't be replaced.
A matching socket isn't the only requirement. The motherboard's chipset and firmware must also support the processor, so check the board's compatibility list before upgrading.
Motherboard Chipsets
The chipset works alongside the processor to manage communication with storage, USB ports, networking, and some expansion slots. It decides features such as:
How many USB ports, SATA ports, and M.2 slots the board can offer
How many PCIe lanes are available beyond those provided by the processor
Whether the processor and memory can be overclocked
Support for features like faster networking and newer USB standards
Chipsets come in tiers within each generation, from entry-level to high-end. Higher-tier chipsets usually add more connectivity and expansion. Each processor generation pairs with a specific family of chipsets, such as the Intel 800 series for Intel Core Ultra 200S desktop processors.
Motherboard Form Factors
A motherboard's form factor sets its size, the layout of its mounting holes, and how many slots it can fit. It also determines which cases it fits into.
Form factor | Size | Typical expansion | Common uses |
Extended ATX (E-ATX) | Larger than ATX; exact size varies | The most slots and connectors | High-end gaming builds and workstations |
ATX | 12 x 9.6 in. | Several PCIe slots and up to 4 memory slots | Mid and full tower desktops |
microATX | 9.6 x 9.6 in. | Fewer PCIe slots, often up to 4 memory slots | Compact towers and everyday desktops |
Mini-ITX | 6.7 x 6.7 in. | One PCIe slot and usually 2 memory slots | Small form factor and compact builds |
Larger boards offer more room for expansion, while smaller boards suit compact cases. Many prebuilt desktops, all-in-ones, and mini PCs use custom-sized motherboards designed for their specific case, which may not fit standard cases. Learn more about tower desktops and the computer form factor buying guide.
Motherboard Expansion Slots and Connectors
PCIe slots come in different sizes, labeled by the number of data lanes they use: x1, x4, x8, and x16. A graphics card typically uses a full-length x16 slot, while smaller cards like network or capture cards use x1 or x4 slots. A slot's physical length doesn't always match its lanes, so a full-length slot may be wired with fewer lanes. Learn more about PCIe slots and ports and interfaces.
M.2 slots hold compact SSDs and, on some boards, wireless cards. Each M.2 slot supports specific drive lengths and interfaces, so check whether a slot supports NVMe, SATA, or both. Learn more about storage.
Motherboard Firmware: BIOS and UEFI
The motherboard stores firmware that runs before the operating system. Older computers used a basic input/output system (BIOS), while modern computers use the Unified Extensible Firmware Interface (UEFI), though many people still call it the BIOS. The firmware checks the hardware at startup, loads the operating system, and lets you adjust settings such as boot order and security options. Firmware updates can add support for new processors and fix security issues. Learn more about drivers and firmware.
Laptop and Prebuilt Motherboards
Laptop motherboards are custom designs built to fit a specific chassis. The processor is usually soldered to the board, and memory and storage may be soldered too, which limits upgrades. Prebuilt desktops often use custom boards that fit their case and power supply. Check your product's service documentation on HP Support to see which parts you can upgrade.
What to Check When Choosing a Motherboard
Socket and chipset: Must support the processor you plan to use, now and in the future.
Form factor: Must fit your case.
Memory support: Check the memory type, number of slots, and maximum capacity.
Storage: Count M.2 slots and SATA ports, and check PCIe generation support.
Expansion: Make sure there are enough PCIe slots for your graphics card and other cards.
Connectivity: Look at rear USB ports, networking, and built-in Wi-Fi.
Frequently Asked Questions About Motherboards
What does a motherboard do?
A motherboard connects all of a computer's components and lets them communicate. It holds the processor, memory, and storage, provides slots for expansion cards, distributes power, and stores the firmware that starts the computer.
What is the difference between a CPU socket and a chipset?
A CPU socket is the physical connector that holds the processor and determines which processors fit. A chipset is a set of controllers on the motherboard that manages connections to storage, USB, and expansion slots and determines many of the board's features.
Can you upgrade a motherboard?
A desktop motherboard can be replaced if the new board fits the case and supports the other components. A new board often requires a compatible processor and memory as well. Laptop motherboards are custom designs and generally aren't upgraded.
What is the most common motherboard size?
ATX is the most common motherboard size for full-size desktops, measuring 12 x 9.6 in. MicroATX is popular for compact towers, and Mini-ITX suits small form factor builds.
Related Components Topics
Computer components: the main parts of a computer and how they work together
Processors (CPU): cores, threads, clock speed, and generations
Memory (RAM): RAM types, speed, capacity, and dual channel
Power supplies: wattage, efficiency ratings, and modular designs
