USSR Soviet Russian Magnetic Ferrite Core Memory Module MF-4 9 Kb 1981 For Sale
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USSR Soviet Russian Magnetic Ferrite Core Memory Module MF-4 9 Kb 1981:
$20.82
Ferrite CoreMemory Module MF-4
Made in the USSR in Oct-81
The board outside dimensions: 15.5x 13 cm
Weight: 100 g
Capacity: 1 tiny ferrite toroid= 1 bit
A 64 x 64 x 18 core memoryplate stores 73728 bit (9 Kb) of data
Condition: used vintagecondition. There are areas with broken rings on the plane. Please see picturesattached.The top cap has been removed to show very tiny rings
Offered storage core plateis an early example of magnetic-core storage — devices consisting of an arrayof magnetic cores.Magnetic-core memory was the predominantform of random-access computer memory for 20 years (circa 1955-75).
Magnetic core — a tiny ferrite toroid of ahard magnetic material that can be magnetized in either of two directionsformerly used in a random access memory to store one bit of data; nowsuperseded by semiconductor memories.
The most common form of core memory, X/Yline coincident-current – used for the main memory of a computer, consists of alarge number of small ferrite (ferromagnetic ceramic) toroids — cores— heldtogether in a grid structure (each grid called a plate), with wires woventhrough 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 eachplate could be accessed in one cycle, so each machine word in an array of wordswas spread over a stack of plates. Each plate would manipulate one bit of aword in parallel, allowing the full word to be read or written in one cycle.
To read a bit of core memory, the circuitrytries 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 thecore is unaffected.
·If the bit was previously 1, then the core changesmagnetic polarity. This change, after a delay, induces a voltage pulse into theSense line.
Detecting such a pulse means that the bitcontained 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 thatreads the contents of a core erases those contents.
To write a bit of core memory, the circuitryassumes 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 aredriven, with current in the opposite direction as for the read operation. Aswith the read, the core at the intersection of the X and Y lines changesmagnetic polarity.
·To write a 0 bit (in other words, to inhibit thewriting of a 1 bit), the same amount of current is also sent through theInhibit line. This reduces the net current flowing through the respective coreto half the select current, inhibiting change of polarity.
Core memory is non-volatile storage – it canretain its contents indefinitely without power. It is also relativelyunaffected by EMP and radiation. These were important advantages for someapplications like first generation industrial programmable controllers,military installations and vehicles like fighter aircraft, as well asspacecraft, and led to core being used for a number of years after availabilityof semiconductor MOS memory.
To know more about Magnetic-core memoryonecanturnto Wikipedia and to other sources
Questions are welcome if I missed anything in thedescription or additional information is needed. If you would like anadditional photo of this item, please feel free to email me, I\'ll be happy toassist you
Shipment
I send an item during 2 businessdays after payment is received. I ship worldwide with some exceptions viaRussian Post.Shippingfrom Russiais $10 and usually takes nothing less than 30 business days
Please, note: terms of delivery can changedepending on work of mail — but I am not responsible for it
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Thankyou for offerding very much!
