Magnetic Core Memory - Hewlett-Packard



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About this Artwork

This artwork celebrates the invention of the magnetic core memory. Before the proliferation of solid-state memory chips such as the Intel 1103 DRAM, core memory dominated the computer industry as the memory technology of choice.

Core Memory was invented by Jay Forrester in 1951. Core, the forerunner of today's solid state RAM, was quickly implemented as the memory of choice for all computers, and dominated until the early 70s. Binary information was represented in core by magnetizing the magnetic rings, or cores, with one of two different polarities. Each core's polarity could be detected and then magnetized again. These two polarities represented 1s and 0s.

Once ubiquitous in computers in the 60’s and 70’s, core memory was replaced in the early 70’s by solid state DRAM (Dynamic Random Access Memory) chips, such as the Intel 1103. The term “core” for a computer’s memory is still sometimes used. A formatted report of the contents of a computer’s memory is still referred to as a Core Dump. One of the useful properties of core memory was that, being magnetic, it was non-volatile, meaning its contents did not change when power was removed. Solid state DRAM systems lose their contents when power is removed and mimicked this retaining ability by using battery backups. Today, flash memories provide this functionality.

This core plane was used in Hewlett Packard’s 2110 series minicomputers from the late 60’s. This is an early core and based on four-wire technology. The wires are X, Y, Sense, and Inhibit. In latter 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 a magnetic core plane from the 1960's Hewlett-Packard 2114, 2115, 2116 mini-computer series. 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.