Possibly the single most successful minicomputer design in history, a favorite of hackers for many years, and the first major Unix machine, The first PDP-11s (the 11/15 and 11/20) shipped in 1970 from DEC; the last (11/93 and 11/94) in 1990. Along the way, the 11 gave birth to the VAX, strongly influenced the design of microprocessors such as the Motorola 6800 and Intel 386, and left a permanent imprint on the C language (which has an odd preference for octal embedded in its syntax because of the way PDP-11 machine instructions were formatted). There is a history site.