Editing Motherboard (section)

==Design==
[[File:386DX40 MB Jaguar V.jpg|thumb|The Octek Jaguar V motherboard from 1993.<ref>{{cite web |url=http://redhill.net.au/b/b-93.html |title=Golden Oldies: 1993 mainboards |access-date=June 27, 2007 |url-status=live |archive-url=https://web.archive.org/web/20070513024500/http://www.redhill.net.au/b/b-93.html |archive-date=May 13, 2007}}</ref> This board has few onboard peripherals, as evidenced by the 6 slots provided for [[ISA bus|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.]]
[[File:Samsung galaxy s2 internal2.JPG|thumb|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 card|video]] display and [[sound card|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 [[bus (computing)|buses]] and external components. This chipset determines, to an extent, the features and capabilities of the motherboard.

Modern motherboards include:
* [[CPU socket]]s (or CPU slots) in which one or more [[microprocessor]]s may be installed. In the case of CPUs in [[ball grid array]] packages, such as the [[VIA Nano]] and the [[Goldmont Plus]], the CPU is directly soldered to the motherboard.<ref>{{cite web |url=http://www.makeuseof.com/tag/cpu-socket-types-explained-from-socket-5-to-bga-makeuseof-explains/ |title=CPU Socket Types Explained: From Socket 5 To BGA [MakeUseOf Explains] |access-date=April 12, 2015 |date=January 25, 2013 |url-status=live |archive-url=https://web.archive.org/web/20150407165233/http://www.makeuseof.com/tag/cpu-socket-types-explained-from-socket-5-to-bga-makeuseof-explains/ |archive-date=April 7, 2015}}</ref>
* 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 [[LPDDR]]x.
* The [[chipset]] which forms an interface between the [[CPU]], [[main memory]], and peripheral buses
* [[Non-volatile memory]] chips (usually [[flash memory]] in modern motherboards) containing the system's [[firmware]] or [[BIOS]]
* The [[clock generator]] which produces the system [[clock signal]] to synchronize the various components
* Slots for [[expansion card]]s (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}}, some [[graphics card]]s (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.<ref>{{cite web |url=http://www.techpowerup.com/articles/overclocking/psu/116 |author=W1zzard |title=Pinout of the PCI-Express Power Connector |publisher=techPowerUp |date=April 6, 2005 |access-date=October 2, 2013 |url-status=live |archive-url=https://web.archive.org/web/20131004215221/http://www.techpowerup.com/articles/overclocking/psu/116 |archive-date=October 4, 2013}}</ref>
* Connectors for hard disk drives, optical disc drives, or solid-state drives, typically [[SATA]] and [[NVMe]]

Additionally, nearly all motherboards include logic and connectors to support commonly used input devices, such as [[USB]] for [[computer mouse|mouse devices]] and [[computer keyboard|keyboards]]. Early [[personal computer]]s such as the [[Apple II]] and [[IBM 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 the [[IBM PCjr]]. Additional peripherals such as [[disk controller]]s and [[serial port]]s were provided as expansion cards.

Given the high [[thermal design power]] of high-speed computer CPUs and components, modern motherboards nearly always include [[heat sink]]s and mounting points for [[computer fan|fan]]s to dissipate excess heat.

===Form factor===
{{main|Motherboard form factor}}
Motherboards are produced in a variety of sizes and shapes called [[motherboard form factor|form factors]], some of which are specific to individual computer manufacturers. However, the motherboards used in IBM-compatible systems are designed to fit various [[computer case|case]] sizes. {{As of|2024}}, most [[desktop computer]] motherboards use the [[ATX]] standard form factor — even those found in [[Macintosh]] and [[Sun Microsystems|Sun]] computers, which have not been built from commodity components. A case's motherboard and [[Power supply unit (computer)|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 computer]]s (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===
[[File:Motherboard diagram.svg|thumb|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 circuit]]s, it is now possible to include support for many [[peripheral]]s on the motherboard. By combining many functions on one [[printed circuit board|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. The ''integrated peripherals'' may also be called ''onboard devices''.
* [[Disk controller]]s for [[SATA]] drives, and historical [[parallel ATA|PATA]] drives
* Historical [[floppy-disk controller]]
* [[Graphics processing unit#Integrated graphics|Integrated graphics controller]] supporting [[2D computer graphics|2D]] and [[3D computer graphics|3D]] graphics, with [[VGA]], [[DVI]], [[HDMI]], [[DisplayPort]], and [[TV-out|TV]] output
* [[Sound card#Integrated sound hardware on PC motherboards|Integrated sound card]] supporting 8-channel (7.1) audio and [[S/PDIF]] output
* [[Ethernet]] [[network controller]] for connection to a [[LAN]] and to receive [[Internet]]
* [[USB]] controller
* [[Wireless network interface controller]]
* [[Bluetooth]] controller
* Temperature, voltage, and fan-speed sensors that allow [[software]] to monitor the health of computer components.
* Other onboard devices, such as [[PMIC]]

===Peripheral card slots===
A typical motherboard will have a different number of connections, depending on its standard and [[computer form factor|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 [[conventional PCI|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 (although this 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 [[Scalable Link Interface|SLI]] (for [[Nvidia]]) and [[ATI CrossFire|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===
[[File:EBMotherboard.JPG|thumb|A motherboard of a Vaio E series laptop (right)]]
[[File:MicroATX Motherboard with AMD Athlon Processor 2 Digon3.jpg|thumb|A microATX motherboard with some faulty capacitors]]
{{Main|Computer cooling}}

Motherboards are generally [[air cooling|air cooled,]] with [[heat sink]]s often mounted on larger chips in modern motherboards.<ref>{{cite web |last1=Karbo |first1=Michael |title=The CPU and the motherboard |url=http://www.karbosguide.com/books/pcarchitecture/chapter26.htm |publisher=Karbos Guide |access-date=June 21, 2015 |url-status=live |archive-url=https://web.archive.org/web/20150427024227/http://www.karbosguide.com/books/pcarchitecture/chapter26.htm |archive-date=April 27, 2015}}</ref> Insufficient or improper cooling can cause damage to the internal components of the computer, or even cause it to [[crash (computing)|crash]]. [[Passive cooling]], or a single fan mounted on the [[power supply unit (computer)|power supply]], was sufficient for many desktop computer CPU's until the late 1990s; since then, most have required [[CPU fan]]s mounted on [[heat sink]]s, due to rising clock speeds and power consumption. Most motherboards have connectors for additional [[computer fan]]s 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.<ref>{{cite web |title=Temperatures |url=https://sites.google.com/site/visualbios/advanced/cooling/temperatures |website=Intel® Visual BIOS Wiki |access-date=June 21, 2015 |url-status=live |archive-url=https://web.archive.org/web/20150621093332/https://sites.google.com/site/visualbios/advanced/cooling/temperatures |archive-date=June 21, 2015}}</ref> Alternatively, computers can use a [[water-cooling#Computer usage|water cooling]] system instead of many fans.

Some [[small form factor]] computers and [[home theater PC]]s 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 [[electronic component|component]]s 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 [[Computer hardware|hardware]] but to aging [[capacitor]]s on PC motherboards.<ref>''[[c't|c't Magazine]]'', vol. 21, pp. 216–221. 2003.</ref> Ultimately, this was shown to be the result of a faulty electrolyte formulation,<ref>{{cite web |url=http://www.spectrum.ieee.org/WEBONLY/resource/feb03/ncap.html |archive-url=https://web.archive.org/web/20030219071949/http://www.spectrum.ieee.org/WEBONLY/resource/feb03/ncap.html |archive-date=February 19, 2003 |first1=Yu-Tzu |last1=Chiu |first2=Samuel K. |last2=Moore |title=Faults & Failures: Leaking Capacitors Muck up Motherboards |publisher=IEEE Spectrum |date=January 31, 2003 |access-date=October 2, 2013}}</ref> an issue termed [[capacitor plague]].

Modern motherboards use [[electrolytic capacitor]]s to filter the [[direct current|DC]] power distributed around the board. These capacitors age at a temperature-dependent rate, as their water based [[electrolyte]]s 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 {{convert|105|C|abbr=on}},<ref>{{cite web |url=http://www.low-esr.com/endurance.asp |title=Capacitor lifetime formula |publisher=Low-esr.com |access-date=October 2, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130915011312/http://low-esr.com/endurance.asp |archive-date=September 15, 2013}}</ref> their expected design life roughly doubles for every {{convert|10|C-change|abbr=on}} below this. At {{convert|65|C|abbr=on}} a lifetime of 3 to 4 years can be expected. However, many manufacturers deliver substandard capacitors,<ref>Carey Holzman ''The healthy PC: preventive care and home remedies for your computer'' McGraw-Hill Professional, 2003 {{ISBN|0-07-222923-3}} page 174</ref> 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 {{convert|95|C|abbr=on}}, effectively doubling the motherboard lifetime.

Mid-range and high-end motherboards, on the other hand, use [[Capacitor types#Comparison of types|solid capacitors]] exclusively. For every 10&nbsp;°C less, their average lifespan is multiplied approximately by three, resulting in a 6-times higher lifetime expectancy at {{convert|65|C|abbr=on}}.<ref>{{cite web |url=http://www.gigabyte.com/webpage/8/article_02_all_solid.htm |title=-- GIGABYTE, --Geeks Column of the Week – All Solid Capacitor |website=www.gigabyte.com |access-date=May 6, 2017 |url-status=live |archive-url=https://web.archive.org/web/20170327102017/http://www.gigabyte.com/webpage/8/article_02_all_solid.htm |archive-date=March 27, 2017}}</ref> These capacitors may be rated for 5000, 10000 or 12000 hours of operation at {{convert|105|C|abbr=on}}, 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]].