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A motherboard (sometimes alternatively known as the mainboard, system board, planar board or logic board, or colloquially, a mobo) is a printed circuit board (PCB) found in all modern computers which holds many of the crucial components of the system, such as the central processing unit (CPU) and memory, and provides connectors for other peripherals.
Motherboard specifically refers to a PCB with expansion capability – the board is the “mother” of all components attached to it, which often include embedded systems, which are not true motherboards.)
Prior to the advent of the peripherals were housed on individual printed circuit boards which plugged into the backplate.
During the late 1980s and 1990s, it became economical to move an increasing number of peripheral functions onto the motherboard. In the late 1980s, motherboards began to include single ICs (called computer graphics typically retained only the graphics card as a separate component.
The early pioneers of motherboard manufacturing were DFI, and a number of Taiwan-based manufacturers.
The most popular computers such as the 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.
A motherboard provides the electrical connections by which the other components of the system communicate. Unlike a backplane, it also connects the central processing unit and hosts other subsystems and devices.
A typical peripheral devices may be attached to the motherboard as plug-in cards or via cables, in modern computers 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, at a minimum:
- citation needed]
- Slots into which the system’s main memory is to be installed (typically in the form of DRAM chips)
- A chipset which forms an interface between the CPU’s front-side bus, main memory, and peripheral buses
- A clock signal to synchronize the various components
- Slots for expansion cards (these 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. Most disk drives also connect to the power supply via dedicated connectors.
Additionally, nearly all motherboards include logic and connectors to support commonly used input devices, such as serial ports were provided as expansion cards.
Given the high fans to dissipate excess heat.
 CPU sockets
A Intel x86 architecture. A CPU socket type and motherboard chipset must support the CPU series and speed.
 Integrated peripherals
With the steadily declining costs and size of small form factor and budget computers.
- Disk controllers for a floppy disk drive, up to 2 PATA drives, and up to 6 SATA drives (including RAID 0/1 support)
- integrated graphics controller supporting 2D and 3D graphics, with VGA and TV output
- integrated sound card supporting 8-channel (7.1) audio and S/PDIF output
- Mbit networking
- USB 2.0 controller supporting up to 12 USB ports
- IrDA controller for infrared data communication (e.g. with an IrDA-enabled cellular phone or printer)
- Temperature, voltage, and fan-speed sensors that allow software to monitor the health of computer components
Expansion cards to support all of these functions would have cost hundreds of dollars even a decade ago; however, as of April 2007[update] such highly integrated motherboards are available for as little as $30 in the US.
 Peripheral card slots
A typical motherboard of 2012 will have a different number of connections depending on its standard.
A standard ATX motherboard will typically have two or three PCI-E 16x connection for a graphics card, one or two legacy PCI slots for various expansion cards, and one or two PCI-E 1x (which has superseded PCI-Express 16x connection for graphics cards, and a varying number of PCI and PCI-E 1x slots. It can sometimes also have a PCI-E 4x slot. (This varies between brands and models.)
Some motherboards have two or more PCI-E 16x slots, to allow more than 2 monitors without special hardware, or use a special graphics technology called ATI). 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, et cetera.
 Temperature and reliability
Motherboards are generally water-cooling system instead of many fans.
Some 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. Ultimately this was shown to be the result of a faulty electrolyte formulation, an issue termed capacitor plague.
Motherboards use  which significantly reduce life expectancy. Inadequate case cooling and elevated temperatures easily exacerbate this problem. It is possible, but tedious and time-consuming, to find and replace failed capacitors on PC motherboards.
 Form factor
Motherboards are produced in a variety of sizes and shapes called 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 due to the large number of integrated components.
 Bootstrapping using the BIOS
Motherboards contain some program counter with the address of the boot ROM and start executing ROM instructions. These instructions displayed system information on the screen, ran memory checks, and then loaded an operating system from an external or peripheral device (disk drive). If none was available, then the computer would perform tasks from other memory stores or display an error message, depending on the model and design of the computer and version of the BIOS.
Most modern motherboard designs use a Power-On Self Test (POST) may include testing some of the following things:
- Video adapter
- Cards inserted into slots, such as conventional PCI
- Floppy drive
- hardware monitoring
- BIOS setup configuration
- network controller
- Optical drives: DVD-ROM
- SCSI hard drive
- hard disk
- Security devices, such as a fingerprint reader or the state of a latch switch to detect intrusion
- USB devices, such as a memory storage device
On recent motherboards, the BIOS may also patch the central processor microcode if the BIOS detects that the installed CPU is one in for which errata has been published.
 See also
- Accelerated Graphics Port
- Computer case screws
- List of computer hardware manufacturers
- Single-board computer
- Switched-mode power supply applications
- Paul Miller. “Apple sneaks new logic board into whining MacBook Pros” (2006). Engadget. http://www.engadget.com/2006/07/08/apple-sneaks-new-logic-board-into-whining-macbook-pros/. Retrieved 2008-10-23.
- “Golden Oldies: 1993 mainboards”. http://redhill.net.au/b/b-93.html. Retrieved 2007-06-27.
- “RS485M-M (V1.0)”. http://www.ecs.com.tw/ECSWebSite/Products/ProductsDetail.aspx?DetailID=654&CategoryID=1&DetailName=Feature&MenuID=46&LanID=9. Retrieved 2007-06-27.
- c’t Magazine, vol. 21, pp. 216-221. 2003.
- Yu-Tzu Chiu, Samuel K. Moore “Faults & Failures: Leaking Capacitors Muck up Motherboards” (2003-02-19) IEEE Spectrum accessed 2008-03-10
- Capacitor lifetime formula
- Carey Holzman The healthy PC: preventive care and home remedies for your computer McGraw-Hill Professional, 2003 ISBN 0-07-222923-3 page 174
|Wikimedia Commons has media related to: Computer motherboards|
- Motherboards at the Open Directory Project
- List of motherboard manufacturers and links to BIOS updates
- What is a motherboard?
- The Making of a Motherboard: ECS Factory Tour
- The Making of a Motherboard: Gigabyte Factory Tour
- Front Panel I/O Connectivity Design Guide – v1.3 (pdf file) (February 2005)