Motherboard

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Motherboard for a desktop personal computer, showing the typical components and interfaces that are found on a motherboard. This model follows the Baby AT (form factor), used in many desktop PCs. Vlb.jpg
Motherboard for a desktop personal computer, showing the typical components and interfaces that are found on a motherboard. This model follows the Baby AT (form factor), used in many desktop PCs.

A motherboard (also called mainboard, main circuit board, [1] or mobo) 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.

Contents

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 daughtercards: 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 Computer-motherboard.jpg
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.


History

Prior to the invention of the microprocessor, the digital computer consisted of multiple printed circuit boards in a card-cage case with components connected by a backplane, a set of interconnected sockets. 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. 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/2 keyboard and mouse, floppy disk drive, serial ports, and parallel ports. By the late 1970s, 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. 386DX40 MB Jaguar V.jpg
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 Samsung galaxy s2 internal2.JPG
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.

Modern motherboards include:

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 PC Jr. 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.

Form factor

Motherboards are produced in a variety of sizes and shape called computer form factor, 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, 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 Motherboard diagram.svg
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.

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.

In newer motherboards, the M.2 slots are for SSD and/or Wireless network interface controller.

Temperature and reliability

A motherboard of a Vaio E series laptop (right) EBMotherboard.JPG
A motherboard of a Vaio E series laptop (right)
A microATX motherboard with some faulty capacitors MicroATX Motherboard with AMD Athlon Processor 2 Digon3.jpg
A microATX motherboard with some faulty capacitors

Motherboards are generally air cooled with heat sinks often mounted on larger chips in modern motherboards. [5] 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 their 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. [6] 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. [7] Ultimately this was shown to be the result of a faulty electrolyte formulation, [8] an issue termed capacitor plague.

Standard 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), [9] 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, [10] 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). [11] 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 Super I/O or Embedded Controller.

Bootstrapping using the Basic Input/Output System

Motherboards contain a ROM (and later EPROM, EEPROM, NOR flash) to initialize hardware devices, and loads an operating system from the peripheral device. 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, displays system information on the screen, performed RAM checks, and then loaded an operating system from a peripheral device. If none 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.

Most modern motherboard designs use a BIOS, stored in an EEPROM or NOR flash chip soldered to or socketed on the motherboard, to boot an operating system. When the computer is powered on, the BIOS firmware tests and configures memory, circuitry, and peripherals. This Power-On Self Test (POST) may include testing some of the following things:

Many motherboards now use a successor to BIOS called UEFI. It became popular after Microsoft began requiring it for a system to be certified to run Windows 8. [12] [13]

See also

Related Research Articles

Backplane

A backplane 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 as a backbone 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.

BIOS Firmware

In computing, BIOS is firmware used to perform hardware initialization during the booting process, and to provide runtime services for operating systems and programs. The BIOS firmware comes pre-installed on a personal computer's system board, and it is the first software to run when powered on. 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.

Bus (computing) System that transfers data between components within a computer

In computer architecture, a bus is a communication system that transfers data between components inside a computer, or between computers. This expression covers all related hardware components and software, including communication protocols.

Industry Standard Architecture 16-bit internal bus

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.

VESA Local Bus Expansion bus for 486 PCs

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.

Expansion card Circuit board able to be connected to a computer system to add functionality

In computing, an expansion card is a printed circuit board that can be inserted into an electrical connector, or expansion slot on a computers motherboard, backplane or riser card to add functionality to a computer system.

Amiga 2000

The Amiga 2000, or A2000, is a personal computer released by Commodore in March 1987. It was introduced as a "big box" expandable variant of the Amiga 1000 but quickly redesigned to share most of its electronic components with the contemporary Amiga 500 for cost reduction. Expansion capabilities include two 3.5" drive bays and one 5.25" bay that can be used by a 5.25" floppy drive, a hard drive, or CD-ROM once they became available.

Single-board computer Computer whose components are on a single printed circuit board

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.

Amiga 4000 Commodore computer

The Commodore Amiga 4000, or A4000, is the successor of the A2000 and A3000 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.

Chipset Set of electronic components in an integrated circuit

In a computer system, a chipset is a set of electronic components in an integrated circuit known as a "Data Flow Management System" that manages the data flow between the processor, memory and peripherals. It is usually found on the motherboard. 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.

Northbridge (computing) One of the two chips in the core logic chipset architecture on a PC motherboard

A northbridge or host bridge is one of the two chips in the core logic chipset architecture on a PC motherboard, the other being the southbridge. Unlike the southbridge, the northbridge is connected directly to the CPU via the front-side bus (FSB) and is thus responsible for tasks that require the highest performance. The northbridge, also known as Memory Controller Hub, is usually paired with a southbridge. In systems where they are included, these two chips manage communications between the CPU and other parts of the motherboard, and constitute the core logic chipset of the PC motherboard.

Southbridge (computing) One of the two chips in the core logic chipset architecture on a PC motherboard

The southbridge is one of the two chips in the core logic chipset on a personal computer (PC) motherboard, the other being the northbridge. The southbridge typically implements the slower capabilities of the motherboard in a northbridge/southbridge chipset computer architecture. In systems with Intel chipsets, the southbridge is named I/O Controller Hub (ICH), while AMD has named its southbridge Fusion Controller Hub (FCH) since the introduction of its Fusion AMD Accelerated Processing Unit (APU) while moving the functions of the Northbridge onto the CPU die, hence making it similar in function to the Platform hub controller.

HPE Integrity 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.

Intel 810 Chipset by Intel

The Intel i810 chipset was released by Intel in early 1999 with the code-name "Whitney" as a platform for the P6-based Socket 370 CPU series, including the Pentium III and Celeron processors. Some motherboard designs include Slot 1 for older Intel CPUs or a combination of both Socket 370 and Slot 1. It targeted the low-cost segment of the market, offering a robust platform for uniprocessor budget systems with integrated graphics. The 810 was Intel's first chipset design to incorporate a hub architecture which was claimed to have better I/O throughput and an integrated GPU, derived from the Intel740.

Amiga 1200

The Amiga 1200, or A1200, is a personal computer in the Amiga computer family released by Commodore International, aimed at the home computer market. It was launched on October 21, 1992, at a base price of £399 in the United Kingdom and $599 in the United States.

Computer hardware Physical components of a computer

Computer hardware includes the physical parts of a computer, such as the case, central processing unit (CPU), monitor, mouse, keyboard, computer data storage, graphics card, sound card, speakers and motherboard.

PICMG 1.0 is a PICMG specification that defines a CPU form factor and corresponding backplane connectors for PCI-ISA passive backplanes. This standard moves components typically located on the motherboard to a single plug-in card. PICMG 1.0 CPU Cards look much like standard ISA cards with extra gold finger connections for the ISA bus and the root PCI bus. The "motherboard" is replaced with a simple "passive backplane" that has only PCI and ISA connectors attached to it. These backplane connections include a dedicated system slot of the PICMG 1.0 CPU and various connections for standard ISA and PCI peripheral cards. This backplane is simple and robust, with a very low likelihood of failure, given its passive nature. This allows a much lower Mean Time to Repair than classic computer motherboard approaches, as electronics associated with CPUs can be replaced without having to remove peripheral devices.

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.

References

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  10. Carey Holzman The healthy PC: preventive care and home remedies for your computer McGraw-Hill Professional, 2003 ISBN   0-07-222923-3 page 174
  11. "-- GIGABYTE, --Geeks Column of the Week - All Solid Capacitor". www.gigabyte.com. Archived from the original on March 27, 2017. Retrieved May 6, 2017.
  12. "Windows Hardware Certification Requirements for Client and Server Systems". Microsoft. January 2013. 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.
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