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Memory Stack Circuit Module

Technical Information

Catalogue No: C1371
Category: Unknown
Object Type: Module/Sub-Assembly/Component
Object Name: Memory Stack Circuit Module
Part No: 51385 D6 74389
Serial No: H-03-018670
Manufacturer: Data General
Division: Unknown
Year of Manufacture: circa 1970
Width (mm):
Height (mm):
Depth (mm):
Weight (g):
Location: Rack RAA03 [Main Store]

P/N 51385 D6 74389
S/N H-03-018670
DGC Nova
16k Memory Stack
Copyright © 1972 by
Data General Corp
(all rights reserved)


This "mattress" of core memory is from an early 1970s Data General Nova computer. This was some of the highest density core but it was not long before integrated circut technology replaced it as the storage medium of choice. Core stores did have the advantage of having a high resistance to radiation so the medium was retained for many years in a military environment.
The Date code on the board is handwritten as part of the Serial No. and it was probably made in Mexico. 32 integrated circuits surround the memory board, which flips open. On the 15 inch by 15 inch plug-in circuit board consisting of 70 integrating circuits, 16 transistors, and a myriad of discrete components (carbon and wire wound resistors, mica, disc, and tantalum capacitors, variable trimpots, semiconductor diodes, etc.) This plug-in circuit board consists of two 50 gold plated edge connectors (double sided).
It is not known why this item was found at Rochester nor what it was used for.

Magnetic-core memory was the predominant form of random-access computer memory for 20 years between about 1955 and 1975. Such memory is often just called core memory, or rope core memory and also core plane.

Core uses tiny magnetic toroids (rings), the cores, through which wires are threaded to write and read information. Each core represents one bitof information. The cores can be magnetized in two different ways (clockwise or counterclockwise) and the bit stored in a core is zero or one depending on that core's magnetization direction. The wires are arranged to allow for an individual core to be set to either a one or a zero and for its magnetization to be changed by sending appropriate electric current pulses through selected wires. The process of reading the core causes the core to be reset to a zero, thus erasing it. This is called destructive readout. When not being read or written, the cores maintain the last value they had, even when power is turned off. This makes them nonvolatile.

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