TABLE OF CONTENTS Let's start with a little history. The notion of a computer "bus" evolved in the early 1960s along with the minicomputer. At that time, the minicomputer was a radical departure in computer architecture. Previously, most computers had been one-of-a-kind, custom built machines with relatively few peripherals a paper tape reader and punch, a teletype, a line printer and, if you were lucky, a disk. The peripheral interface logic was tightly coupled to the processor logic.
The integrated circuit shrank the CPU from a refrigerator-sized cabinet down to one or two printed circuit boards. The interface electronics to peripheral devices shrank accordingly. Now computers could be cranked out on an assembly line, but only if they could be assembled efficiently. The engineers of the day quickly recognized the obvious solution design all the boards to a common electrical and protocol interface specification. Assembling the computer is now just a matter of plugging boards into a backplane consisting of connectors and a large number of parallel wires.
The computer bus also solved a marketing problem. After all, there's no point in mass producing computers unless you can sell them. A single company possesses limited expertise and resources to address only a small segment of the potential applications for computers. The major minicomputer vendors solved this problem by making their bus specifications public to encourage third party vendors to build compatible equipment addressing different market segments. Digital Equipment Corp. (DEC) was an early and very successful proponent of this strategy.
