Plessey Peripheral Systems Core Storage

This core storage dates from about 1975.
It is perhaps the finest core storage in our collection.
At this time LSI (Large Scale Integration) memory was being manufactured.
The advantage of core storage was that it was not volatile.
When the power was removed core storage retained its information, LSI memory lost it.

Complete Module

This is the complete module. It consists of a "mother" and "daughter" board.
The larger board underneath, with its gold plated connectors at the top, is the mother board.
The smaller, with the soldered printed circuits is the back of the daughter board.

The whole weighed 1.1Kg and measures 416mm x 227mm.

Mus.Cat. NEWUC:2002.4.1 Mnfctr: Plessey Peripheral Systems Date: 1975 (circa) Ser. No: 5612 Part No: 700944-100D
Comp: Mother Board Width: 416 mm Depth: 11 mm Height: 227 mm Weight: 744 g

Front of Mother Board

This is the front of the mother board with the circuitry to do the addressing, reading and writing.

The two rows of 16 circular silver components are transistors.
The black rectangular components contain silicon chips.
So this is one of the last core storage modules before solid logic technology took over.

Rear of Mother Board

Turning the mother board back over and unplugging the daughter board
reveals the rear of the mother board.

Mus.Cat. NEWUC:2002.4.2 Mnfctr: Plessey Peripheral Systems Date: 1975 (circa) Ser. No: 5737 Part No: 700945-100B
Comp: Daughter Board Width: 328 mm Depth: 200 mm Height: 18 mm Weight: 1.1 Kg

Turning the daughter board over reveals the core storage plane.
It has 64 core mats each being in two halves.

Each core mat is 64 x 64 cores. So the total number of cores is 262,144.
That is 32Kbytes. It is organized as 16K x 16bit words.

Core Storage plane

Going in close we can see the two halves of a core mat.
The top half has cores angled in pairs of columns //\\
whereas the bottom half has them angled \\//.

Every core is threaded by a horizontal wire from side to side
and a vertical wire from top to bottem,
then one of two third wires that threads every other column in the core mat.

Close-up of Core Mat

The vertical, horizontal, and third wires are all in red and green pairs.

The horizontal wires are 1/4 mm apart, the vertical are 0.6mm apart.

The cores themselves have an outside diameter of 0.6mm,
therefore the hole in the middle must be about 0.4mm through which are three wires.

Close-up of Core Mat

The third wire is fed in bunches, then splits to go across as two pairs, each to thread two core mats.

It is mind boggling to think how this core storage was made.
Each core mat is about the size of two of my thumbnails, over 2000 cores per thumbnail.
It has got to be made by human hands, and it is not a "one off", but a mass produced object.

The fineness of it is incredible.

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