Ferrite Core Memory Plate
Made in USSR in 1980
Plate size: 11.5 x11.5 cm (~ 4.8 x 4.8 inch in US unit of length)
The board outside dimensions: 11.5 x 11.5 cm
The frame outside dimensions (without pins): 10.0 x 10.0 cm (3.94 x 3.94 inch in US unit of length)
The dimension of the core plate itself: 7.3 x 7.3 cm (2.87 x 2.87 inch in US unit of length)
As it is written in operation manual toroid dimensions are 1.0 x 0.7 x 0.35 mm
Capacity: 1 tiny ferrite toroid = 1 bit
A 64 x 64 core memory plate stores 4096 bits of data
Condition: nice condition with just a pair of broken wires. Please see pictures attached (defects are shown on the last two photos )
Magnetic-core memory was the predominant form of random-access computer memory for 20 years (circa 1955-75).
Magnetic core — a tiny ferrite toroid of a hard magnetic material that can be magnetized in either of two directions formerly used in a random access memory to store one bit of data; now superseded by semiconductor memories.
The most common form of core memory, X/Y line coincident-current – used for the main memory of a computer, consists of a large number of small ferrite (ferromagnetic ceramic) toroids — cores— held together in a grid structure (each grid called a plate), with wires woven through the holes in the cores' middle. On a given plate there are four wires, X, Y, Sense and Inhibit. Each toroid stores one bit (a 0 or 1). One bit in each plate could be accessed in one cycle, so each machine word in an array of words was spread over a stack of plates. Each plate would manipulate one bit of a word in parallel, allowing the full word to be read or written in one cycle.
To read a bit of core memory, the circuitry tries to flip the bit to whatever polarity the machine regards as the 0 state, by driving the selected X and Y lines that intersect at that core.
If the bit was already 0, the physical state of the core is unaffected.
If the bit was previously 1, then the core changes magnetic polarity. This change, after a delay, induces a voltage pulse into the Sense line.
Detecting such a pulse means that the bit contained 1. Absence of the pulse means that the bit contained 0.
Following any such read, the bit contains 0. This illustrates why core memory features destructive reads: Any operation that reads the contents of a core erases those contents.
To write a bit of core memory, the circuitry assumes there has been a read operation and the bit is in the 0 state.
To write a 1 bit, the selected X and Y lines are driven, with current in the opposite direction as for the read operation. As with the read, the core at the intersection of the X and Y lines changes magnetic polarity.
To write a 0 bit (in other words, to inhibit the writing of a 1 bit), the same amount of current is also sent through the Inhibit line. This reduces the net current flowing through the respective core to half the select current, inhibiting change of polarity.
Core memory is non-volatile storage – it can retain its contents indefinitely without power. It is also relatively unaffected by EMP and radiation. These were important advantages for some applications like first generation industrial programmable controllers, military installations and vehicles like fighter aircraft, as well as spacecraft, and led to core being used for a number of years after availability of semiconductor MOS memory.
To know more about Magnetic-core memory one
can turn to Wikipedia and to other sources
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