Magnetic Core Memory - UNIVAC - 8K bits - Eckert & Mauchly


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About this Artwork

This artwork celebrates the invention of the magnetic core memory. Before computer memory chips, memory systems for computers used varied technologies, were difficult to implement, were very expensive, and were unfortunately unreliable. Magnetic core memory was the first workable, large scale memory system. Iron donuts (cores) were arranged in grids. Early 1960s UNIVAC computers used 4-wire core systems such as the one above. X/Y wires were used to select an individual core. The combined current in the two wires was required to magnetize the core to represent a single binary digit, one or zero. One core, one bit.

The UNIVAC was a computer created by J. Presper Eckert and John Mauchly who were the inventors of the ENIAC, the first general-purpose digital computer. Early UNIVAC computers made extensive use of core memory. The core memory in this artwork can hold 8K bits of information. It was likely used in UNIVAC's military computers, due to the use of an anti-corrosive material applied to the core plane.

This is an early core and is based on four-wire technology. The wires are X, Y, Sense, and Inhibit. In later cores, the Sense and Inhibit wires were combined since they were used at different times: the Sense during the read cycle, and Inhibit during the write cycle. The cores can be magnetized to either “North” or “South” polarity. These polarities were used to represent 1s and 0s. To make the core “flip” to one pole or the other, a certain threshold of electrical current was needed to generate the required magnetic field. The X and Y wires were used to select one of the cores, and each wire carried ½ of the current needed to make the switch. To write a bit to a core, the X and Y wires are activated. This action would result in a 1 always being written, but in the case of a 0 to be written, the Inhibit wire was activated with a ½ level reverse current to cancel out the X/Y pair. To read a bit, once again the X and Y wires were activated. If the core was a 0, it then “flipped” to a 1. This change caused a spike in current on the Sense wire and this was interpreted as a 0. If the core was already a 1, then nothing happened on the Sense wire and this was interpreted as a 1. This reading operation was “destructive” and was followed by a write operation to restore the bit to its original condition. Multiple planes were stacked together so that multiple bits could be accessed in parallel to create nibbles, bytes, and words for the computer’s architecture.

The artwork includes the UNIVAC magnetic core plane. The image is based on a microscopic photograph of the core memory, focused on one of the cores. The artwork contains information on the history and operation of core memory.



    The artwork is framed in an 11"x14" black shadow box frame, with glass. All framing materials are acid-free. A narrative about the artwork that includes the artist’s signature is placed on the back of the artwork.

    Please note:  The look of the artifacts in the artworks may vary, each piece is unique.