system, such as a modern computer. It is also known as a mainboard, baseboard, system

board, or, on Apple computers, a logic board, and is sometimes abbreviated as mobo.[1]

Most after-market motherboards produced today are designed for so-called IBM-compatible

computers, which hold over 96% of the personal computer market today.[2] Motherboards for

IBM-compatible computers are specifically covered in the PC motherboard article.

The basic purpose of the motherboard, like a backplane, is to provide the electrical and

logical connections by which the other components of the system communicate.

A typical desktop computer is built with the microprocessor, main memory, and other

essential components on the motherboard. Other components such as external storage,

controllers for video display and sound, and peripheral devices are typically attached to

the motherboard via edge connectors and cables, although in modern computers it is

increasingly common to integrate these "peripherals" into the motherboard.

 

The motherboard of a typical desktop consists of a large PCB. It holds electronic

components and interconnects, as well as physical connectors (sockets, slots, and headers)

into which other computer components may be inserted or attached.

Most motherboards include, at a minimum:

sockets (or slots) in which one or more microprocessors (CPUs) are installed[4]
slots into which the system's main memory is installed (typically in the form of DIMM

modules containing DRAM chips)
a chipset which forms an interface between the CPU's front-side bus, main memory, and

peripheral buses
non-volatile memory chips (usually Flash ROM in modern motherboards) containing the

system's firmware or BIOS
a clock generator which produces the system 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 and circuits, which receive electrical power from the computer power

supply and distribute it to the CPU, chipset, main memory, and expansion cards.[5]
 
The Octek Jaguar V motherboard from 1993.[6] This board has 6 ISA slots but few onboard

peripherals, as evidenced by the lack of external connectors.Additionally, nearly all

motherboards include logic and connectors to support commonly-used input devices, such as

PS/2 connectors for a mouse and keyboard. Early personal computers such as the Apple II or

IBM PC included only this minimal peripheral support on the motherboard. 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 heatsinks and mounting points for fans to dissipate

excess heat.

 

Prior to the advent of the Apple II in 1977, a computer was usually built in a case or

mainframe with components connected by a backplane consisting of a set of slots themselves

connected with wires. The CPU, memory and I/O peripherals were housed on individual PCBs or

cards which plugged into the backplane.

With the arrival of the microprocessor, it became more cost-effective to place the

backplane connectors, processor and glue logic onto a single "mother" board, with video,

memory and I/O functions on "child" cards — hence the terms "motherboard" and

daughterboard. The Apple II computer featured a motherboard with 8 expansion slots.

During the late 1980s and 1990s, it became economical to move an increasing number of

peripheral functions onto the motherboard (see above). In the late 1980s, motherboards

began to include single ICs (called Super I/O chips) capable of supporting a set of

low-speed peripherals: keyboard, mouse, floppy disk drive, serial ports, and parallel

ports. As of the early 2000s, many motherboards support a full range of 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 retain only the graphics

card as a separate component.

The early pioneers of motherboard manufacturing were Micronics, Mylex, AMI, DTK, Hauppauge,

Orchid Technology, Elitegroup, DFI, and a number of Taiwan-based manufacturers.

It can be argued that the motherboard industry was born by IBM in 1981 with the release

their entry level 5150 Personal Computer (IBM PC) which was based on a motherboard. The

motherboard provided an Intel 4.77MHz 8088 with 16K bytes of on-board memory, expandable to

640K through the use of plug-in memory boards, eight 8-bit ISA expansion connectors,

cassette tape port and keyboard port. All other I/O such as the interface for 160K 5-1/4"

floppy drives, serial and parallel ports were provided by plug-in boards. IBM approached

Digital Research about using DR/DOS as an operating system but was rebuffed. IBM approached

Microsoft and licensed PC-DOS. Microsoft released PC-DOS 1.1 in 1982 by retaining rights to

the operating system allowing them to sell it to other manufacturers.

IBM published the schematics and I/O map allowing the birth of the clone motherboard

industry.