Patent GB-864463-A (GB)
Title: Improvements in magnetic core storage devices
IPC: G11C11/08
Filed: 1957-11-19
Abstract: 864,463. Circuits employing bi-stable magnetic elements. INTERNATIONAL BUSINESS MACHINES CORPORATION. Nov. 19, 1957 [Nov. 19, 1956], No. 35997/57. Class 40 (9). [Also in Groups XIX and XXXV] A magnetic core storage device has a magnetic core which at one section is divided by apertures 20, 12, 16 to provide four flux paths a, b, c, d, and is provided with a winding 20 linking only path b, a winding 15 linking only path c, and an output winding 14 which links path c and/or path d. The device may be used in a manner to permit destructive readout (Figs. 3C, 3D, 3E) when the state of the core is determined by the position of the main flux (shown dotted) to the right or the left of aperture 12, or in a manner to permit non-destructive readout (Figs. 7C, 7D, 7E) when the state of the core is indicated by the direction of the main flux (clockwise or counter-clockwise). Destructive readout.-The magnetic core is constructed so that sections a + b and c + d are each equal to section C. A main flux is set up in the core by a winding 22 which flux lies to the left of aperture 12. Biasing currents flow continuously through windings 18 and 15 to produce fields directed downwards in the paths b and c; that in path c producing a counterclockwise field round aperture 16 so that the flux pattern of Fig. 3E is produced. If now winding 18 is pulsed to produce an upward flux in path b (overcoming the biasing current) part of the main flux is transferred from path b to path d. On the termination of this pulse the bias current in this winding transfers the main flux in path a to path c giving the flux pattern of Fig. 3C. This flux pattern is regarded as a datum condition representing a binary " 0." To write a " 1 " a pulse is applied to the winding 15 overcoming the bias current. This sets up the flux pattern of Fig. 30 and on termination of the signal when the bias current once again takes effect, the flux pattern of Fig. 3E is produced. To write a " 0 " when the Fig. 3C pattern has been established, the winding 18 is pulsed which merely changes the direction of the localized flux round the aperture 20, the Fig. 3C pattern being re-established by the biasing current after the signal, and the main flux is unaffected. To interrogate the core, the winding 18 is pulsed; if a " 0 " is stored there is no change in the main flux and no output voltage; if a " 1 " is stored (Fig. 3E) then the pulse transfers part of main flux to the right of aperture 12 and the biasing current transfers the rest to give the Fig. 3C pattern and an output in winding 14. The information is therefore destroyed. The core may be rectangular, the biasing currents may be supplied by separate windings and the windings 18, 15 may each be duplicated so as to be suitable for coincident half current reading and writing. Suitable relative values of half currents and bias currents are necessary for proper operation. Non-destructive readout.-Winding 22 sets up a clockwise main flux to write a binary " 0 " and a counter-clockwise flux for a binary " 1." Reading is performed by pulsing first winding 18 which now acts as a set-up winding and then winding 15 which is a read winding, the pulses producing downward fluxes in paths b and c respectively. With a binary " 0 " established pulses in windings 18 and 15 produce the Fig. 7C flux pattern and a repeated reading gives no output. With a binary " 1 " established (Fig. 7D) pulsing the set-up winding 18 transfers main flux to path d and establishes a Fig. 7E pattern and the subsequent pulsing of winding 15 reverses the direction of the localized flux round aperture 12, thereby giving an output pulse. Repeated readings (each comprising a set-up pulse in winding 18 followed by a read pulse in winding 15) provide an output pulse. Windings 22 and 18 may be duplicated to permit coincident half-current operation, and such a construction forms the element of an array shown in Fig. 9. Half select pulses are supplied from drivers 80a, 80b, 80c, 82a, 82b, 82c to set a chosen core. The set-up windings are fed from row and column set-up drivers 96a, 96b, 96c, 98a, 98b, 98c and the read windings from a read driver 90. Coincident pulsing of the set-up windings of a selected core followed by pulsing the read winding interrogates that core. Specifications 845,431 and 848,833 are referred to.