System Bus - Background

Background

Many early electronic computers were based on the First Draft of a Report on the EDVAC report published in 1945. In what became known as the Von Neumann architecture, a central control unit and arithmetic logic unit (ALU, which he called the central arithmetic part) were combined with computer memory and input and output functions to form a stored program computer. The Report presented a general organization and theoretical model of the computer, however, not the implementation of that model. Soon designs integrated the control unit and ALU into what became known as the central processing unit (CPU).

Computers in the 1950s and 1960s were generally constructed in an ad-hoc fashion. For example, the CPU, memory, and input/output units were each one or more cabinets connected by cables. Engineers used the common techniques of standardized bundles of wires and extended the concept as backplanes were used to hold printed circuit boards in these early machines. The name "bus" was already used for "bus bars" that carried electrical power to the various parts of electric machines, including early mechanical calculators. The advent of integrated circuits vastly reduced the size of each computer unit, and buses became more standardized. Standard modules could be interconnected in more uniform ways and were easier to develop and maintain.