A motherboard (also called mainboard, maincircuit board, MB, mboard, backplane board, base board, system board, mobo, or, in Apple computers, logic board) is the main printed circuit board (PCB) in general-purpose computers and other expandable systems. It holds and allows communication between many of the crucial electronic components of a system, such as the central processing unit (CPU) and memory, and provides connectors for other peripherals. Unlike a backplane, a motherboard usually contains significant sub-systems, such as the central processor, the chipset's input/output and memory controllers, interface connectors, and other components integrated for general use.
Motherboard means specifically a PCB with expansion capabilities. As the name suggests, this board is often referred to as the mother of all components attached to it, which often include peripherals, interface cards, and daughterboards: sound cards, video cards, network cards, host bus adapters, TV tuner cards, IEEE 1394 cards, and a variety of other custom components.
Dell Precision T3600 System Motherboard, used in professional CAD Workstations. Manufactured in 2012
Similarly, the term mainboard describes a device with a single board and no additional expansions or capability, such as controlling boards in laser printers, television sets, washing machines, mobile phones, and other embedded systems with limited expansion abilities.
Motherboard for a personal desktop computer; showing the typical components and interfaces which are found on a motherboard. This model follows the Baby AT (form factor), used in many desktop PCs.
Prior to the invention of the microprocessor, the CPU of a digital computer consisted of multiple circuit boards in a card-cage case with components connected by a backplane containing a set of interconnected sockets into which the circuit boards are plugged. In very old designs, copper wires were the discrete connections between card connector pins, but printed circuit boards soon became the standard practice. The central processing unit (CPU), memory, and peripherals were housed on individually printed circuit boards, which were plugged into the backplane.
In older microprocessor-based systems, the CPU and some support circuitry would fit on a single CPU board, with memory and peripherals on additional boards, all plugged into the backplane. The ubiquitous S-100 bus of the 1970s is an example of this type of backplane system.
The most popular computers of the 1980s such as the Apple II and IBM PC had published schematic diagrams and other documentation which permitted rapid reverse engineering and third-party replacement motherboards. Usually intended for building new computers compatible with the exemplars, many motherboards offered additional performance or other features and were used to upgrade the manufacturer's original equipment.
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 called Super I/O chips) capable of supporting a set of low-speed peripherals: PS/2keyboard and mouse, floppy disk drive, serial ports, and parallel ports. By the late 1990s, many personal computer motherboards included consumer-grade embedded audio, video, storage, and networking functions without the need for any expansion cards at all; higher-end systems for 3D gaming and computer 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 the tablet computer and the netbook). Memory, processors, network controllers, power source, and storage would be integrated into some systems.
Design
The Octek Jaguar V motherboard from 1993. This board has few onboard peripherals, as evidenced by the 6 slots provided for ISA cards and the lack of other built-in external interface connectors. Note the large AT keyboard connector at the back right is its only peripheral interface.The motherboard of a Samsung 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 the central processing unit and hosts other subsystems and devices.
A typical desktop computer has its microprocessor, main memory, and other essential components connected to the motherboard. Other components such as external storage, controllers for video display and sound, 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.
An important component of a motherboard is the microprocessor's supporting chipset, which provides the supporting interfaces between the CPU and the various buses and external components. This chipset determines, to an extent, the features and capabilities of the motherboard.
Memory slots into which the system's main memory is to be installed, typically in the form of DIMM modules containing DRAM chips. Can be DDR3, DDR4, DDR5, or onboard LPDDRx.
The chipset which forms an interface between the CPU, main memory, and peripheral buses
Slots for expansion cards (the interface to the system via the buses supported by the chipset)
Power connectors, which receive electrical power from the computer power supply and distribute it to the CPU, chipset, main memory, and expansion cards. As of 2007[update], some graphics cards (e.g. GeForce 8 and Radeon R600) require more power than the motherboard can provide, and thus dedicated connectors have been introduced to attach them directly to the power supply.[3]
Connectors for hard disk drives, optical disc drives, or solid-state drives, typically SATA and NVMe now[when?]
Additionally, nearly all motherboards include logic and connectors to support commonly used input devices, such as USB for mouse devices and keyboards. Early personal computers such as the Apple II or IBM PC included only this minimal peripheral support on the motherboard. Occasionally video interface hardware was also integrated into the motherboard; for example, on the Apple II and rarely on IBM-compatible computers such as the IBM PCjr. Additional peripherals such as disk controllers and serial ports were provided as expansion cards.
Given the high thermal design power of high-speed computer CPUs and components, modern motherboards nearly always include heat sinks and mounting points for fans to dissipate excess heat.
Motherboards are produced in a variety of sizes and shapes called form factors, some of which are specific to individual computer manufacturers. However, the motherboards used in IBM-compatible systems are designed to fit various case sizes. As of 2005[update], most desktop computer motherboards use the ATX standard form factor — even those found in Macintosh and Sun computers, which have not been built from commodity components. A case's motherboard and power 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 a microATX 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.
CPU sockets
A CPU socket (central processing unit) or slot is an electrical component that attaches to a printed 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 and server computers (laptops typically use surface mount CPUs), particularly those based on the Intel x86 architecture. A CPU socket type and motherboard chipset must support the CPU series and speed.
Integrated peripherals
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 of integrated circuits, it is now possible to include support for many peripherals on the motherboard. By combining many functions on one PCB, the physical size and total cost of the system may be reduced; highly integrated motherboards are thus especially popular in small form factor and budget computers.
Temperature, voltage, and fan-speed sensors that allow software to monitor the health of computer components.
Peripheral card slots
A typical motherboard will have a different number of connections depending on its standard and form factor.
A standard, modern ATX motherboard will typically have two or three PCI-Express x16 connection for a graphics card, one or two legacy PCI slots for various expansion cards, and one or two PCI-E x1 (which has superseded PCI). A standard EATX motherboard will have two to four PCI-E x16 connection for graphics cards, and a varying number of PCI and PCI-E x1 slots. It can sometimes also have a PCI-E x4 slot (will vary between brands and models).
Some motherboards have two or more PCI-E x16 slots, to allow more than 2 monitors without special hardware, or use a special graphics technology called SLI (for Nvidia) and Crossfire (for AMD). These allow 2 to 4 graphics cards to be linked together, to allow better performance in intensive graphical computing tasks, such as gaming, video editing, etc.
Motherboards are generally air cooled with heat sinks often mounted on larger chips in modern motherboards.[4] Insufficient or improper cooling can cause damage to the internal components of the computer, or cause it to crash. Passive cooling, or a single fan mounted on the power supply, was sufficient for many desktop computer CPU's until the late 1990s; since then, most have required CPU fans mounted on heat sinks, due to rising clock speeds and power consumption. Most motherboards have connectors for additional computer fans and integrated temperature sensors to detect motherboard and CPU temperatures and controllable fan connectors which the BIOS or operating system can use to regulate fan speed.[5] Alternatively computers can use a water cooling system instead of many fans.
Some small form factor computers and home 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 other components to allow for heat sink placement.
A 2003 study found that some spurious computer crashes and general reliability issues, ranging from screen image distortions to I/O read/write errors, can be attributed not to software or peripheral hardware but to aging capacitors on PC motherboards.[6] Ultimately this was shown to be the result of a faulty electrolyte formulation,[7] an issue termed capacitor plague.
Modern motherboards use electrolytic capacitors to filter the DC power distributed around the board. These capacitors age at a temperature-dependent rate, as their water based electrolytes slowly evaporate. This can lead to loss of capacitance and subsequent motherboard malfunctions due to voltage instabilities. While most capacitors are rated for 2000 hours of operation at 105°C (221°F),[8] 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,[9] 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, use solid 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).[10] 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 a super I/O chip or an embedded controller.
Microcomputers such as the Apple II and IBM PC used ROM chips mounted in sockets on the motherboard. At power-up, the central processor unit would load its program counter with the address of the Boot ROM and start executing instructions from the Boot ROM. These instructions initialized and tested the system hardware, displayed system information on the screen, performed RAM checks, and then attempts to boot an operating system from a peripheral device. If no peripheral device containing an operating system was available, then the computer would perform tasks from other ROM stores or display an error message, depending on the model and design of the computer. For example, both the Apple II and the original IBM PC had Cassette BASIC (ROM BASIC) and would start that if no operating system could be loaded from the floppy disk or hard disk.
The boot firmware in modern IBM PC compatible motherboard designs contains either a BIOS, as did the boot ROM on the original IBM PC, or UEFI. UEFI is a successor to BIOS that became popular after Microsoft began requiring it for a system to be certified to run Windows 8.[12][13]
When the computer is powered on, the boot firmware tests and configures memory, circuitry, and peripherals. This Power-On Self Test (POST) may include testing some of the following things:
A backplane or backplane system is a group of electrical connectors in parallel with each other, so that each pin of each connector is linked to the same relative pin of all the other connectors, forming a computer bus. It is used to connect several printed circuit boards together to make up a complete computer system. Backplanes commonly use a printed circuit board, but wire-wrapped backplanes have also been used in minicomputers and high-reliability applications.
In computing, BIOS is firmware used to provide runtime services for operating systems and programs and to perform hardware initialization during the booting process. The BIOS firmware comes pre-installed on an IBM PC or IBM PC compatible's system board and exists in some UEFI-based systems to maintain compatibility with operating systems that do not support UEFI native operation. The name originates from the Basic Input/Output System used in the CP/M operating system in 1975. The BIOS originally proprietary to the IBM PC has been reverse engineered by some companies looking to create compatible systems. The interface of that original system serves as a de facto standard.
Industry Standard Architecture (ISA) is the 16-bit internal bus of IBM PC/AT and similar computers based on the Intel 80286 and its immediate successors during the 1980s. The bus was (largely) backward compatible with the 8-bit bus of the 8088-based IBM PC, including the IBM PC/XT as well as IBM PC compatibles.
The VESA Local Bus is a short-lived expansion bus introduced during the i486 generation of x86 IBM-compatible personal computers. Created by VESA, the VESA Local Bus worked alongside the then-dominant ISA bus to provide a standardized high-speed conduit intended primarily to accelerate video (graphics) operations. VLB provides a standardized fast path that add-in (video) card makers could tap for greatly accelerated memory-mapped I/O and DMA, while still using the familiar ISA bus to handle basic device duties such as interrupts and port-mapped I/O. Some high-end 386DX motherboards also had a VL-Bus slot.
In computing, an expansion card is a printed circuit board that can be inserted into an electrical connector, or expansion slot on a computer's motherboard to add functionality to a computer system. Sometimes the design of the computer's case and motherboard involves placing most of these slots onto a separate, removable card. Typically such cards are referred to as a riser card in part because they project upward from the board and allow expansion cards to be placed above and parallel to the motherboard.
A single-board computer (SBC) is a complete computer built on a single circuit board, with microprocessor(s), memory, input/output (I/O) and other features required of a functional computer. Single-board computers are commonly made as demonstration or development systems, for educational systems, or for use as embedded computer controllers. Many types of home computers or portable computers integrate all their functions onto a single printed circuit board.
The Amiga 4000, or A4000, from Commodore is the successor of the Amiga 2000 and Amiga 3000 computers. There are two models: the A4000/040 released in October 1992 with a Motorola 68040 CPU, and the A4000/030 released in April 1993 with a Motorola 68EC030.
In a computer system, a chipset is a set of electronic components on one or more integrated circuits that manages the data flow between the processor, memory and peripherals. The chipset is usually found on the motherboard of computers. Chipsets are usually designed to work with a specific family of microprocessors. Because it controls communications between the processor and external devices, the chipset plays a crucial role in determining system performance.
Mini-ITX is a 170 mm × 170 mm motherboard form factor developed by VIA Technologies in 2001. Mini-ITX motherboards have been traditionally used in small-configured computer systems. Originally, Mini-ITX was a niche standard designed for fanless cooling with a low power consumption architecture, which made them useful for home theater PC systems, where fan noise can detract from the cinema experience.
In computing, a northbridge is one of two chips comprising the core logic chipset architecture on motherboards for older personal computers. A northbridge is connected directly to a CPU via the front-side bus (FSB) to handle high-performance tasks, and is usually used in conjunction with a slower southbridge to manage communication between the CPU and other parts of the motherboard.
The southbridge is one of the two chips in the core logic chipset on older personal computer (PC) motherboards, the other being the northbridge. As of 2023, most personal computer devices no longer use a set of two chips, and instead have a single chip acting as the 'chipset', for example Intel's Z790 chipset.
HPE Integrity Servers is a series of server computers produced by Hewlett Packard Enterprise since 2003, based on the Itanium processor. The Integrity brand name was inherited by HP from Tandem Computers via Compaq.
A power-on self-test (POST) is a process performed by firmware or software routines immediately after a computer or other digital electronic device is powered on.
An Option ROM for the PC platform is a piece of firmware that resides in ROM on an expansion card, which gets executed to initialize the device and (optionally) add support for the device to the BIOS. In its usual use, it is essentially a driver that interfaces between the BIOS API and hardware. Technically, an option ROM is firmware that is executed by the BIOS after POST and before the BIOS boot process, gaining complete control of the system and being generally unrestricted in what it can do. The BIOS relies on each option ROM to return control to the BIOS so that it can either call the next option ROM or commence the boot process. For this reason, it is possible for an option ROM to keep control and preempt the BIOS boot process. The BIOS generally scans for and initializes option ROMs in ascending address order at 2 KB address intervals within two different address ranges above address C0000h in the conventional (20-bit) memory address space; later systems may also scan additional address ranges in the 24-bit or 32-bit extended address space.
The AMD 700 chipset series is a set of chipsets designed by ATI for AMD Phenom processors to be sold under the AMD brand. Several members were launched in the end of 2007 and the first half of 2008, others launched throughout the rest of 2008.
I/O Controller Hub (ICH) is a family of Intel southbridge microchips used to manage data communications between a CPU and a motherboard, specifically Intel chipsets based on the Intel Hub Architecture. It is designed to be paired with a second support chip known as a northbridge. As with any other southbridge, the ICH is used to connect and control peripheral devices.
Computer hardware includes the physical parts of a computer, such as the central processing unit (CPU), random access memory (RAM), motherboard, computer data storage, graphics card, sound card, and computer case. It includes external devices such as a monitor, mouse, keyboard, and speakers.
Intel 5 Series is a computing architecture introduced in 2008 that improves the efficiency and balances the use of communication channels in the motherboard. The architecture consists primarily of a central processing unit (CPU) and a single chipset. All motherboard communications and activities circle around these two devices.
This glossary of computer hardware terms is a list of definitions of terms and concepts related to computer hardware, i.e. the physical and structural components of computers, architectural issues, and peripheral devices.
↑ "Windows Hardware Certification Requirements for Client and Server Systems". Microsoft. January 2013. Archived from the original on November 5, 2021. Retrieved July 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.
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
