Backplane

A backplane is a circuit board (usually a printed circuit board) that connects several connectors in parallel to each other, so that each pin of each connector is linked to the same relative pin of all the other connectors, forming a computer bus. It is used as a backbone to connect several printed circuit board cards together to make up a complete computer system. One popular early computer system that used this approach was called the S-100 bus because the connectors used had one hundred pins. Some computers like the Apple II and the IBM PC integrated an internal backplane for expansion cards.

IBM PC) or S-100 style where all the connectors were connected to a common bus. Because of limitations inherent in the PCI specification for driving slots, backplanes are now offered as passive and active. Passive backplanes offer no active bus driving circuitry. Active backplanes include chips which buffer the various signals to the slots.

In any case, a backplane is generally differentiated from a motherboard by the lack of on-board processing power where the CPU is on a plug-in card.

See the bottom of for a good explanation of single board computers and backplanes.--