Motherboard

Motherboard

A motherboard (sometimes alternatively known as the mainboard, system board, planar board or logic board,^[1] or colloquially, a mobo) is a printed circuit board (PCB) found in computers and other expandable systems. It holds many of the crucial components of the system, such as the central processing unit (CPU) and memory, and provides connectors for other peripherals. Unlike a backplane, a motherboard contains significant sub-systems such as the processor.

Motherboard specifically refers to a PCB with expansion capability - the board is the "mother" of all components attached to it, which often include sound cards,video cards, network cards, hard drives or other forms of persistent storage, TV tuner cards, cards providing extra USB or Firewire slots, and a variety of other custom components. (The term mainboard is applied to devices with a single board and no additional expansions or capability - in modern terms this would include controlling boards in televisions, washing machines and other embedded systems, which are not true motherboards.)

History

Prior to the advent of the microprocessor, a computer was usually built in a card-cage case or mainframe with components connected by a backplane consisting of a set of slots themselves connected with wires; in very old designs the wires were discrete connections between card connector pins, but printed circuit boards soon became the standard practice. The Central Processing Unit, memory and 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 Super I/O chips) capable of supporting a set of low-speed peripherals: keyboard, mouse, floppy disk drive, serial ports, andparallel ports. By the late 1990s, many personal computer motherboards supported 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 retained only the graphics card as a separate component.

The most popular computers 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.

Design

Modern motherboards include, at a minimum: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.

• sockets (or slots) in which one or more microprocessors may be installed. In the case of CPUs in BGA packages, such as the VIA C3, the CPU is directly soldered to the motherboard.^{[citation needed]}
• Slots into which the system's main memory is to be 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, 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 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.^[3] Most disk drives also connect to the power supply via dedicated connectors