Rare Vintage Mainframe Ferrite Core Memory 4096 Bytes of 1960s For Sale
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Rare Vintage Mainframe Ferrite Core Memory 4096 Bytes of 1960s:
$295.00
Rare! Vintage Mainframe Ferrite Core Memory 4096 Bytes of 1960sPlate size (approx):5 x 5 inch
The board weighs approximately 0.3 pounds
Capacity:1 tiny ferrite core = 1 bit
A 64 x 64 core memory plate stores 4096 bit of data
CONDITION: excellentcondition without broken wires and missing cores
The heyday of ferritememory was in the 50s and 60s of the last century. Before its appearance, allsorts of exotic devices that were poorly suited for mass use had to be used ascomputer memory devices - oscilloscope tubes, mercury delay lines, etc. Ferritearraysdiffered favorably from them, first of all, in their highest reliability andsmall dimensions. They lasted until the mass development of semiconductorintegrated circuits, with which ferrites could not compete due to their lack oftechnological effectiveness (and, accordingly, price), and later - also thelimited volume of stored information.
For data storage systemsof digital machines, ferrites with nonlinear magnetic characteristics are used- ferrites with a rectangular hysteresis loop (RHL).
These ferrites arespecial in that the cores made from them can be in two stable states ofmagnetization - +B, which corresponds to the code "1", and -B,corresponding to the code "0" in the binary number system.
In order to remagnetize,for example, a ferrite rod or ring, it is necessary to create a magnetic fieldof a certain intensity. If the magnetic field has an intensity less than thethreshold value H, then the ferrite will not remagnetize even with repeated andlong-term application of this magnetic field.
The classic scheme forusing ferrites with RHL for memory devices is based on the coincidence ofhalf-currents, i.e. on the principle that under the action of a magnetic fieldH/2, the coredoes not change its magnetic state, and under the action of a field H, it iscompletely remagnetized.
In this case, the randomaccess memory device is a matrix of toroids through which conductors pass intwo directions - current-carrying buses for exciting magnetic fields and areading winding for removing information codes. In order to simplify thetechnology of matrix production, all toroid windings are made single-turn.
In order to record thecode "1" in any toroid, it is necessary to excite a field H/2 in thebuses at the intersection of which it is located. In the selected toroid, theampere turns of both directions will add up and a field equal to H will act onit.
When recording the code"0", the exciting fields created by the buses x and y are suppliedwith a time shift, or all toroids are supplied with an additional winding,called the unit inhibition winding and designed to create a field of the oppositepolarity to the recording field at the right time, equal to -H/2. The resultingfield in both cases will be equal to H/2 and the toroid will not beremagnetized from the state.
When reading the recordedinformation from the toroid, it is necessary to excite a field of –H/2 usingthe buses intersecting in it. Then the toroid on which the code “1” wasrecorded will be remagnetized from the state +B to the state -B and the emf ofthe signal of the code “1” will be induced on the reading wire. The toroid onwhich the code “0” was recorded will not be remagnetized (will remain in thestate -B) and the emf of the signal will not be induced on the reading wire.
It should be noted thatthe information is destroyed after it is read. To reuse the information in themachine, it must be restored (regenerated).
One reading wire and oneinhibit wire are woven through all the cores. Thus, the matrix allows readingor writing bits only sequentially.
Ferrite cores were alsoused to build read-only memory units. Binary information was recorded in themduring assembly, by appropriately flashing the cores with readout wires. Inthis case, the passage of a wire through the core is equivalent to a binaryone, and the passage of a wire past the core means recording a binary zero.
Memory devices onmagnetic ferrite cores are units consisting of a large number (up to hundredsof thousands) of ferrite ring magnets arranged in regular rows in the form of aflat or spatial lattice.
Each toroidal core isused to store one binary digit: zero or one. The cores are 1-5 mm in diameter(in UScomputers the minimum diameter reached 0.25-0.30 mm).
Soviet memory units on ferrites, as a rule, were devices forprivate use, developed for each product separately and therefore were oflimited circulation.
The exception was theso-called Memory Cubes, which found application in second- and third-generationcomputers, which determined their serial production and standardization.
Despite all theadvantages of memory devices made on ferrite cores, they had a number ofsignificant disadvantages. These disadvantages include:
- high labor intensity ofmanufacturing a numerical block: flashing the cores was an operation that requiredsignificant manual labor;
- the impossibility ofreplacing the core in case of its breakage; if it was necessary to replace onering, it was necessary to re-flash a significant number of cores;
- strong influence of theambient temperature on the properties of the cores, in particular, on the widthof the hysteresis loop;
- the need to return thecores to their original state;
- self-heating of thecores caused by hysteresis losses, which limited the maximum operatingfrequency of the memory device;
- a large number ofcores.
They tried to overcomethese shortcomings both within the framework of traditional schemes - bycomplicating firmware schemes or using multi-winding cores - and by using new,advanced developments for that time. This is how memory devices on multi-hole plates,biaxes, layered ferrites and systems on thin magnetic films appeared. What ischaracteristic, the technological methods of manufacturing such systems(photolithography, vacuum and chemical deposition, etc.) anticipatedsemiconductor production.
But in fact, after the"explosive" development of integrated memory circuits, since themid-70s, ferrite memory systems were used only in those areas where theiradvantages, such as resistance to radiation and electromagnetic interference,were critical - space systems, industrial equipment, etc.
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