Vacuum-tube based computers had modular construction, but individual functions for peripheral devices filled a cabinet, not just a printed circuit board. Processor, memory and I/O cards became feasible with the development of integrated circuits. Expansion cards make processor systems adaptable to the needs of the user by making it possible to connect various types of devices, including I/O, additional memory, and optional features (such as a floating point unit) to the central processor. Minicomputers, starting with the PDP-8, were made of multiple cards communicating through, and powered by, a passive backplane.
Vacuum-tube based computers had modular construction, but individual functions for peripheral devices filled a cabinet, not just a printed circuit board. Processor, memory and I/O cards became feasible with the development of integrated circuits. Expansion cards make processor systems adaptable to the needs of the user by making it possible to connect various types of devices, including I/O, additional memory, and optional features (such as a floating point unit) to the central processor. Minicomputers, starting with the PDP-8, were made of ,multiple cards communicating through and powered by, a passive backplane.