Motherboard
A motherboard (also called mainboard, main circuit board, MB, mboard, backplane board, base board, system board, mobo, or, in Apple computers, logic board) is the main printed circuit board (PCB) in general-purpose computers and other expandable systems. It holds and allows communication between many of the crucial electronic components of a system, such as the central processing unit (CPU) and memory, and provides connectors for other peripherals. Unlike a backplane, a motherboard usually contains significant sub-systems, such as the central processor, the chipset's input/output and memory controllers, interface connectors, and other components integrated for general use.
For other uses, see Motherboard (disambiguation).
Motherboard means specifically a PCB with expansion capabilities. As the name suggests, this board is often referred to as the mother of all components attached to it, which often include peripherals, interface cards, and daughterboards: sound cards, video cards, network cards, host bus adapters, TV tuner cards, IEEE 1394 cards, and a variety of other custom components.
Similarly, the term mainboard describes a device with a single board and no additional expansions or capability, such as controlling boards in laser printers, television sets, washing machines, mobile phones, and other embedded systems with limited expansion abilities.
Motherboards contain a ROM (and later EPROM, EEPROM, NOR flash) that stores firmware that initializes hardware devices and boots an operating system from a peripheral device. The terms bootstrapping and boot come from the phrase "lifting yourself by your bootstraps".[11]
Microcomputers such as the Apple II and IBM PC used ROM chips mounted in sockets on the motherboard. At power-up, the central processor unit would load its program counter with the address of the Boot ROM and start executing instructions from the Boot ROM. These instructions initialized and tested the system hardware, displayed system information on the screen, performed RAM checks, and then attempts to boot an operating system from a peripheral device. If no peripheral device containing an operating system was available, then the computer would perform tasks from other ROM stores or display an error message, depending on the model and design of the computer. For example, both the Apple II and the original IBM PC had Cassette BASIC (ROM BASIC) and would start that if no operating system could be loaded from the floppy disk or hard disk.
The boot firmware in modern IBM PC compatible motherboard designs contains either a BIOS, as did the boot ROM on the original IBM PC, or UEFI. UEFI is a successor to BIOS that became popular after Microsoft began requiring it for a system to be certified to run Windows 8.[12][13]
When the computer is powered on, the boot firmware tests and configures memory, circuitry, and peripherals. This Power-On Self Test (POST) may include testing some of the following things: