Editing Motherboard (section)

==History==
[[File:NeXTcube motherboard.jpg|thumb|Mainboard of a [[NeXTcube]] computer (1990) with microprocessor [[Motorola 68040]] operated at 25 [[MHz]] and a [[digital signal processor]] [[Motorola 56001]] at 25 MHz, which was directly accessible via a connector on the back of the casing]]

Prior to the invention of the [[microprocessor]], the [[CPU]] of a [[Computer|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 board]]s 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), [[primary memory|memory]], and [[peripheral]]s 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/2 port|PS/2]] [[Computer keyboard|keyboard]] and [[Computer mouse|mouse]], [[floppy disk drive]], [[serial port]]s, and [[parallel port]]s. By the late 1990s, many personal computer motherboards included consumer-grade embedded audio, video, storage, and networking functions without the need for any [[expansion card]]s at all; higher-end systems for [[3D computer graphics|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.