What is the main circuit board of a computer that contains the CPU?

January 28, 2005 The motherboard is the main circuit board of a microcomputer. The motherboard contains the connectors for attaching additional boards. Typically, the motherboard contains the CPU, BIOS, memory, mass storage interfaces, serial and parallel ports, expansion slots, and all the controllers required to control standard peripheral devices, such as the display screen, keyboard, and disk drive. Collectively, all these chips that reside on the motherboard are known as the motherboard's chipset. On most PCs, it is possible to add memory chips directly to the motherboard. You may also be able to upgrade to a faster CP by replacing the CPU chip. To add additional core features, you may need to replace the motherboard entirely. (Glossary) “Also known as the logic board, main board, or computer board, the motherboard is the computer's main board and in most cases holds all CPU, memory, and I/O functions or has expansion slots for them”. (Kingston) The motherboard is the most important part of your computer. It is also one of the most compared, critiqued, and reviewed pieces of hardware. Often, on the internet, you'll find reviews and debates over which board is best or which chipset is best. The chipset controls the system and its capabilities. It is the hub of all data transfer. It is a series of chips on the motherboard, easily identified as the largest chips on the board with the exception of the CPU. Chip s...

A rigid, flat board that holds chips and other electronic components. The printed circuit board (PCB) is made of layers, from two to a dozen or more, that interconnect components via copper pathways. The main board in a computer is called the "system board" or "motherboard," while smaller ones that plug into slots on the main board are called "boards" or "cards." See motherboard, expansion card and flexible circuit.

Etched Circuits

The "printed" circuit is an etched circuit. A copper foil is placed over a fiberglass or plastic base of each layer and covered with a photoresist. Light is beamed through a negative image of the circuit paths onto the photoresist, hardening the areas that will remain after etching. When passed through an acid bath, the unhardened areas are washed away, and the finished layers are then glued together. The etching process is also used to create integrated circuits (chips).

Starting in the 1940s

Printed circuit boards (PCBs) were first used in the 1940s to connect discrete components together. By the 1960s, they were widely used in all electronic systems, and as integrated circuits emerged in the 1970s, chips were increasingly mounted on the boards. Today, PCBs hold a few discrete elements but mostly chips, and each chip contains from thousands to billions of transistors (see chip). See surface mount, via and discrete component.

PCI Express slots on a motherboard

A heatsink and fan manage the heat components such as the CPU generate. Typically motherboards offer additional connectivity through a Southbridge chip such as PCI, Serial Advanced Technology Attachment or SATA, Thunderbolt, USB and other interfaces.

The CPU is generally connected to double data rate 3 (DDR3), DDR4, DDR5 or onboard LPDDRx RAM and PCIe. This is done through point-to-point interconnects such as HyperTransport, Intel's QuickPath Interconnect and Ultra Path Interconnect. Choosing a motherboard often determines many features a computer will support.

Motherboard designs in desktop computers typically are the ATX motherboard, which is Intel's improved version of IBM's AT design. Other form factor designers include the following:

• extended ATX
• mini-ATX
• micro ATX
• BTX
• micro BTX
• mini-ITX
• micro ITX
• nano-ITX

Some memory controllers are now built into CPUs; that has eliminated the Northbridge chips that provided memory management from the motherboard. Integrated video has moved from a motherboard slotted peripheral to graphics-enabled CPUs.

AMD's Ryzen has a system-on-a-chip design that also makes the Southbridge chipset optional. This CPU integration has cut motherboard manufacturers' costs. They can offer base systems for workstations and entry-level computers and can design customized implementations for various processors that enable platform upgrades.

Gaming motherboards are made for high-performance computers; they are more powerful and have more features than motherboards for desktop and laptop computers.

A typical motherboard contains the CPU, memory, storage, ROM BIOS, Southbridge and Northbridge chipsets, cooling fans, peripheral connector slots, connectors for peripheral devices, the battery backup and the power connector.

Motherboard components

Each motherboard is designed to support specific components, such as CPUs and memory. They can accommodate most types of hard drives and peripherals.

Motherboards include the following primary components:

• CPU with its logic circuitry that processes the instructions from programs, the operating system and other computer components;
• memory where instructions and data are temporarily stored and executed;
• storage interface for solid-state or hard disk drive for persistent data and application storage;
• ROM BIOS providing non-volatile memory that stores firmware, such as the basic input/output system or BIOS;
• Northbridge chipset that connects CPU, memory, storage and other components;
• Southbridge chipset that connects peripheral elements to the motherboard and connects to the Northbridge;
• cooling fans that maintain a suitable internal operating temperature;
• peripheral connector slots for plugin peripheral cards, such as graphics and communications adapters;
• connectors for peripheral devices such as USB ports and other connectors for external devices;
• the backup battery that ensures key system configuration data is maintained when main power is unavailable; and
• the power connector, connecting to an external power source.

Many other elements comprise a typical motherboard. Think of a motherboard as a large mosaic of electrical connections linking the various parts of a computer.

Learn the essentials of buying server hardware, including what you need to know about server motherboards.

This was last updated in June 2022

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