/ī(-ə)rn āj/
n. In the history of computing, 1961-1971 -- the formative era of commercial mainframe technology, when big iron dinosaurs ruled the earth. These began with the delivery of the first PDP-1, coincided with the dominance of ferrite {core}, and ended with the introduction of the first commercial microprocessor (the Intel 4004) in 1971.
See also Stone Age; compare elder days.