| | | | The main circuit board of a computer, also known as the System Board or Main Board. A complex piece of circuitry on a printed circuit board (PCB) comprising of the main components of the computer and into which other circuit boards can be slotted (similar to a backplane except that a motherboard carries the processor whereas on a backplane the processor is on a separate plug-in card). In addition to the processor, desktop computer motherboards will typically have: the chipset, BIOS ROM, slots to receive memory (RAM), expansion slots such as (depending on the age of the machine) ISA, PCI, PCI-X and and AGP as well as various onboard circuitry which may obviate the need for separate cards - examples include modem, sound, graphics and networking capabilities. Also present are controller circuits and connections for keyboard, mouse, printer and VGA (if graphics are onboard) as well as USB and serial ports and sometimes firewire (IEEE 1394) and IrDA. Other devices such as mass storage media (hard disk drives, tape drives etc) can be connected via cables and/or plug in controller cards. Motherboards come in a range of form factors, which over time have tended to reduce in size. Examples of IBM-PC compatible form factors are: PC/XT (the first IBM PC motherboard), AT, ATX and micro-ATX and there are more specialist types for specialised applications such as servers and thin clients. Laptop/notebook motherboards have all necessary controller circuits built-in because of size constraints, but still offer a route to expansion through external ports e.g. USB and firewire and Cardbus/PCMCIA slots. | | | |
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