1973. The first company to establish a ''de facto'' standard was Altair with the Altair 8800, developed 1974-1975, which later became a multi-manufacturer standard, the S-100 bus. Many of these computers were also passive backplane designs, where all elements of the computer, (processor, memory, and I/O) plugged into a card cage which passively distributed signals and power between the cards.

Proprietary bus