History of RAM

1 Megabit chip - one of the last models developed by VEB Carl Zeiss Jena in 1989

An early type of widespread writable random-access memory was magnetic core memory, developed from 1955 to 1975, and subsequently used in most computers up until the development and adoption of the static and dynamic integrated RAM circuits in the late 1960s and early 1970s. Before this, computers used relays, delay line/delay memory, or various kinds of vacuum tube arrangements to implement "main" memory functions (i.e., hundreds or thousands of bits), some of which were random access, some not. Drum memory could be expanded at low cost but retrieval of non-sequential memory items required knowledge of the physical layout of the drum to optimize speed. Latches built out of vacuum tube triodes, and later, out of discrete transistors, were used for smaller and faster memories such as random-access register banks and registers. Prior to the development of integrated ROM circuits, permanent (or read-only) random-access memory was often constructed using semiconductor diode matrices driven by address decoders, or specially wound core memory planes.