Oxford English Dictionary traces the origin of the wordmotherboard to 1965, its earliest-found attestation occurring in the magazineElectronics.[2] The term alludes to its importance and size compared to the components attached to it, being the "mother of all boards" in a computer system.[3]
Several alternative terms formotherboard have been used in technical documentation and industry practice, includingmainboard,system board,logic board,baseboard, and the informalmobo. These terms are functionally synonymous and reflect regional, corporate, or contextual preferences rather than a coordinated effort to adopt gender-neutral language.[citation needed]
System board was used byIBM in documentation for theIBM PC and its derivatives; however, higher-end models in thePS/2 line, such as theModel 80, used the termplanar instead.Apple commonly useslogic board in its technical documentation for products such as theApple II and theMac.Intel typically usesbaseboard in its technical manuals, though it also usesmotherboard interchangeably.[1] The termmobo is an informal truncation ofmotherboard, popularized by computer enthusiasts and builders in the 1990s.[4]
Before the advent of themicroprocessor, thecentral processing unit (CPU) of acomputer was typically implemented using multipleprinted circuit boards housed in a card cage, interconnected via abackplane—a board containing sockets into which the individual circuit boards were inserted. Early systems used discrete copper wiring between connector pins, but printed circuit boards quickly became the standard. The CPU,main memory, andperipheral components were each located on separate boards connected through the backplane.[citation needed]
With the rise of microprocessors, CPU functionality and supporting circuitry were consolidated onto a single board, while memory and peripherals remained on separate expansion cards plugged into the backplane. A prominent example is theS-100 bus, widely used in 1970s microcomputer systems such as theAltair 8800.
In the 1980s, popular personal computers like theApple II andIBM Personal Computer featured publicly available schematic diagrams and technical documentation[5][6]. This openness enabled rapidreverse engineering and the development of third-party motherboards. These clone and upgrade boards often provided enhanced performance or additional features, and were commonly used to modernize or replace original manufacturer hardware.[citation needed]
The first backplane to qualify as a motherboard was the Planar Breadboard, designed by IBM engineer Patty McHugh and used in the 1981 IBM Personal Computer.[7]
During the late 1980s and early 1990s, it became economical to move an increasing number of peripheral functions onto the motherboard. In the late 1980s, personal computer motherboards began to include single ICs (also calledSuper I/O chips) capable of supporting a set of low-speed peripherals:PS/2keyboard andmouse,floppy disk drive,serial ports, andparallel ports. By the late 1990s, many personal computer motherboards included consumer-grade embedded audio, video, storage, and networking functions without the need for anyexpansion cards at all; higher-end systems for3D gaming andcomputer graphics typically retained only the graphics card as a separate component. Business PCs, workstations, and servers were more likely to need expansion cards, either for more robust functions, or for higher speeds; those systems often had fewer embedded components.
Laptop and notebook computers that were developed in the 1990s integrated the most common peripherals. This even included motherboards with no upgradeable components, a trend that would continue as smaller systems were introduced after the turn of the century (like thetablet computer and thenetbook). Memory, processors, network controllers, power source, and storage would be integrated into some systems.[citation needed]
The Octek Jaguar V motherboard from 1993.[8] This board has few onboard peripherals, as evidenced by the 6 slots provided forISA cards and the lack of other built-in external interface connectors. Note the largeAT keyboard connector at the back right is its only peripheral interface.The motherboard of aSamsung Galaxy SII; almost all functions of the device are integrated into a very small board.
A motherboard provides the electrical connections by which the other components of the system communicate. Unlike a backplane, it also contains thecentral processing unit and hosts other subsystems and devices.
A typicaldesktop computer has itsmicroprocessor,main memory, and other essential components connected to the motherboard. Other components such asexternal storage, controllers forvideo display andsound, and peripheral devices may be attached to the motherboard as plug-in cards or via cables; in modern microcomputers, it is increasingly common to integrate some of these peripherals into the motherboard itself.[citation needed]
An important component of a motherboard is the microprocessor's supportingchipset, which provides the supporting interfaces between the CPU and the variousbuses and external components. This chipset determines, to an extent, the features and capabilities of the motherboard.[citation needed]
Memory slots into which the system's main memory is to be installed, typically in the form ofDIMM modules containingDRAM chips. Can beDDR3,DDR4,DDR5, or onboardLPDDRx. Furthermore, some motherboards have dual memory slots which allows the installation of different memory types, such as eitherDDR2 or DDR3.[10]
Thechipset which forms an interface between theCPU,main memory, and peripheral buses
Slots forexpansion cards (the interface to the system via the buses supported by the chipset)
Power connectors, which receive electrical power from the computerpower supply and distribute it to the CPU, chipset, main memory, and expansion cards. As of 2007[update], somegraphics cards (e.g.GeForce 8 andRadeon R600) require more power than the motherboard can provide, and thus dedicated connectors have been introduced to attach them directly to the power supply.[11]
Connectors for hard disk drives, optical disc drives, or solid-state drives, typicallySATA andNVMe
Additionally, nearly all motherboards include logic and connectors to support commonly used input devices, such asUSB formouse devices andkeyboards. Earlypersonal computers such as theApple II andIBM PC include only this minimal peripheral support on the motherboard. Video interface hardware was also occasionally integrated into the motherboard; for example, on the Apple II. It was even less common on IBM-compatible computers, such as theIBM PCjr. Additional peripherals such asdisk controllers andserial ports were provided as expansion cards.[citation needed]
Given the highthermal design power of high-speed computer CPUs and components, modern motherboards nearly always includeheat sinks and mounting points forfans to dissipate excess heat.[citation needed]
Motherboards are produced in a variety of sizes and shapes calledform factors, some of which are specific to individual computer manufacturers. However, the motherboards used in IBM-compatible systems are designed to fit variouscase sizes. As of 2024[update], mostdesktop computer motherboards use theATX standard form factor — even those found inMacintosh andSun computers, which have not been built from commodity components. A case's motherboard andpower supply unit (PSU) form factor must all match, though some smaller form factor motherboards of the same family will fit larger cases. For example, an ATX case will usually accommodate amicroATX motherboard. Laptop computers generally use highly integrated, miniaturized, and customized motherboards. This is one of the reasons that laptop computers are difficult to upgrade and expensive to repair. Often the failure of one laptop component requires the replacement of the entire motherboard, which is usually more expensive than a desktop motherboard.
ACPU socket (central processing unit) or slot is an electrical component that attaches to aprinted circuit board (PCB) and is designed to house a CPU (also called a microprocessor). It is a special type of integrated circuit socket designed for very high pin counts. A CPU socket provides many functions, including a physical structure to support the CPU, support for a heat sink, facilitating replacement (as well as reducing cost), and most importantly, forming an electrical interface both with the CPU and the PCB. CPU sockets on the motherboard can most often be found in most desktop andserver computers (laptops typically use surface mount CPUs), particularly those based on theIntel x86 architecture. A CPU socket type and the motherboard chipset must support the CPU series and speed.
Block diagram of an early 2000s motherboard, which supports many on-board peripheral functions as well as several expansion slots
With the steadily declining costs and size ofintegrated circuits, it is now possible to include support for manyperipherals on the motherboard. By combining many functions on onePCB, the physical size and total cost of the system may be reduced; highly-integrated motherboards are thus especially popular insmall form factor and budget computers. Theintegrated peripherals may also be calledonboard devices.
A typical motherboard will have a different number of slots, depending on its standard andform factor.
Many motherboards feature two or morePCI Express (PCIe) x16 slots, enabling support for multiple graphics cards or connecting multiple monitors directly without requiring specialized hardware. Some high-end models support multi-GPU technologies such asNvidia'sScalable Link Interface (SLI) andAMD'sCrossFire (formerly ATI CrossFire), which allow two to four graphics cards to operate in parallel, improving performance in graphics-intensive applications like gaming and video editing. However, as modern games and APIs increasingly favor single powerful GPUs, and with both Nvidia and AMD having largely discontinued active support for these technologies, multi-GPU configurations are now less common.
Modern motherboards also feature PCIe x1 and possiblylegacy PCI slots for other peripherals.
A standard, modern ATX motherboard will typically have two or three PCIe x16 slots for a graphics card, one or two legacy PCI slots for various expansion cards, and one or two PCIe x1 slots. A standardEATX motherboard will have two to four PCIe x16 slots for graphics cards, and a varying number of PCI and PCIe x1 slots. It can sometimes also have a PCIe x4 slot (although this will vary between brands and models).
Modern motherboards typically include one or moreM.2 slots—some high-end models offer up to four. These slots support a variety of devices, includingNVMe-basedsolid-state drives (SSDs),SATA-based M.2 SSDs, andwireless network interface controllers (such as Wi-Fi and Bluetooth modules). M.2 provides a compact, high-speed interface that leverages the PCIe or SATA bus, depending on the configuration.
Motherboards are generallyair cooled, withheat sinks often mounted on larger chips in modern motherboards.[12] Insufficient or improper cooling can cause damage to the internal components of the computer, or even cause it tocrash.Passive cooling, or a single fan mounted on thepower supply, was sufficient for many desktop computer CPUs until the late 1990s; since then, most have requiredCPU fans mounted onheat sinks, due to rising clock speeds and power consumption. Most motherboards have connectors for additionalcomputer fans and integrated temperature sensors to detect motherboard and CPU temperatures and controllable fan connectors which theBIOS oroperating system can use to regulate fan speed.[13] Alternatively, computers can use awater cooling system instead of many fans.
Somesmall form factor computers andhome theater PCs designed for quiet and energy-efficient operation boast fan-less designs. This typically requires the use of a low-power CPU, as well as a careful layout of the motherboard and othercomponents to allow for heat sink placement.
A 2003 study found that some spurious computer crashes and general reliability issues, ranging from screen image distortions toI/O read/write errors, can be attributed not tosoftware or peripheralhardware but to agingcapacitors on PC motherboards.[14] Ultimately, this was shown to be the result of a faulty electrolyte formulation,[15] an issue termedcapacitor plague.
Modern motherboards useelectrolytic capacitors to filter theDC power distributed around the board. These capacitors age at a temperature-dependent rate, as their water basedelectrolytes slowly evaporate. This can lead to loss of capacitance and subsequent motherboard malfunctions due tovoltage instabilities. While most capacitors are rated for 2000 hours of operation at 105 °C (221 °F),[16] their expected design life roughly doubles for every 10 °C (18 °F) below this. At 65 °C (149 °F) a lifetime of 3 to 4 years can be expected. However, many manufacturers deliver substandard capacitors,[17] which significantly reduce life expectancy. Inadequate case cooling and elevated temperatures around the CPU socket exacerbate this problem. With top blowers, the motherboard components can be kept under 95 °C (203 °F), effectively doubling the motherboard lifetime.
Mid-range and high-end motherboards, on the other hand, usesolid capacitors exclusively. For every 10 °C less, their average lifespan is multiplied approximately by three, resulting in a 6-times higher lifetime expectancy at 65 °C (149 °F).[18] These capacitors may be rated for 5000, 10000 or 12000 hours of operation at 105 °C (221 °F), extending the projected lifetime in comparison with standard solid capacitors.
In desktop PCs and notebook computers, the motherboard cooling and monitoring solutions are usually based on asuper I/O chip or anembedded controller.
Modern motherboards contain firmware stored in non-volatile memory such asROM,EPROM,EEPROM, orNOR flash, which is responsible for initializing system hardware and loading anoperating system from aboot device. The termsbooting andbootstrapping derive from the metaphor "pulling oneself up by one's bootstraps", reflecting the self-starting nature of the process.[19]
In early microcomputers like theApple II andIBM Personal Computer, firmware was stored in socketedROM chips on the motherboard. Upon power-up, thecentral processing unit (CPU) would load itsprogram counter with the address of the boot ROM and begin executing instructions from it. These instructions performed apower-on self-test (POST), initialized hardware components, displayed system information, verifiedrandom-access memory (RAM), and attempted to locate and load an operating system from a bootable peripheral device. If no such device was found, the system would either execute built-in software from ROM—such asCassette BASIC (commonly known as ROM BASIC)—or display an error message, depending on the model. For instance, both the Apple II and the original IBM PC would launch their built-in BASIC interpreter when no bootable disk was present.
The boot firmware in modernIBM PC compatible motherboard designs contains either aBIOS, as did the boot ROM on the original IBM PC, orUEFI. UEFI is a successor to BIOS that became popular after Microsoft began requiring it for a system to be certified to runWindows 8.[20][21]
When the computer is powered on, the boot firmware tests and configures memory, circuitry, and peripherals. ThisPower-On Self Test (POST) may include testing some of the following things:[citation needed]
^"Windows Hardware Certification Requirements for Client and Server Systems". Microsoft. January 2013.Archived from the original on November 5, 2021. RetrievedJuly 3, 2020.System.Fundamentals.Firmware.CS.UEFISecureBoot.ConnectedStandby ... Platforms shall be UEFI Class Three (see UEFI Industry Group, Evaluating UEFI using Commercially Available Platforms and Solutions, version 0.3, for a definition) with no Compatibility Support Module installed or installable. BIOS emulation and legacy PC/AT boot must be disabled.
