The engineering samples show various size ferrite cores. Core memory, developed by Jay Forrester at M.I.T. and independently by An Wang at Harvard, was first demonstrated in May of 1952, and became the dominant form of computer memory until the mid- to late 1970s. (The last core memory was manufactured in 1980 by DEC). A steady reduction in size and improvements in switching speeds occurred throughout core memory's almost-thirty year lifetime. Core memory was eventually supplanted by semiconductor Random Access Memory (RAM) chips.