Patent GB-875358-A (GB)
Title: Improvements in magnetic core devices
IPC: G06F7/38
Filed: 1958-09-19
Abstract: 875,358. Magnetic storage devices. INTERNATIONAL BUSINESS MACHINES CORPORATION. Sept. 19, 1958 [Sept. 20, 1957], No. 30089/58. Class 38 (2). [Also in Groups XIX and XXXIX] A magnetic core adder or logical device has a square loop core 10 (Fig. 4) having six or more legs, adapted to be switched between two remanent states, which provide flux paths of unequal remanence such that reversal of flux in any one of the left-hand legs always reverses the flux in leg 26, and reversal of flux in two of the left-hand legs reverses the flux in legs 26 and 28. Reversal of flux in all three left-hand legs reverses the flux in legs 26, 28 and 30. The cross-sectional areas of the legs are equal and the cross-sectional area of the yokes is three times this area. The carry output winding 46 of the full adder in Fig. 4 links only leg 28 and is energized by flux reversal in this leg both when two or three of input windings X, Y and Z are energized and when reset winding 44 is subsequently energized to reset the entire core to the clockwise remanence condition (Fig. 1, not shown). Sum output winding 50 links leg 28 oppositely to legs 26 and 30. Owing to the different lengths of the flux paths containing legs 26, 28 and 30, coincident energization of windings X, Y, Z, or of two of them, produce successive pulses of alternating polarity at the terminals of winding 50. To obtain a single output pulse on switching of the legs 26, 28, 30 by energization of reset winding 44, this winding is provided with extra turns linking the longer flux paths. A single sum output pulse can be obtained by connecting winding 50 in series with a winding 60 (Fig. 5) on a toroidal core 62 provided with a write bias winding 64, a read bias winding 66 and an output winding 68. Core 62 is switched from the state produced by a signal in write bias winding 64 when one or three of the input windings X, Y, Z are energized. Winding 78 which links legs 26 and 30 oppositely to leg 28 is energized at input or write time in each cycle. At reset time substantially no output is produced by reversal of flux in legs 26 and 28 any tendency to switch at different rates being inhibited by winding 50. If flux in leg 30 is also reversed because three inputs have been applied, core 62 is switched and a single sum output appears in winding 68. In an alternative arrangement (Fig. 6, not shown) output winding 50 is coupled to a load device through a diode biased during input time to inhibit current flow. Fig. 7 shows the six-legged core wound for use as a logical device with two input windings supplied with inputs P and Q and another energized at input time in each cycle by a clock pulse source Q. An output is obtained when both inputs are present, when only input Q is present and when neither is present. Another arrangement for obtaining the same result is described (Fig. 8, not shown). A further arrangement employing an eight-legged core (Fig. 9, not shown) has four output windings one producing an output when input P but not input Q is present, another when input Q but not input P is present, a third when both input P and input Q are present, when input P is present but not input Q and when neither input P nor input Q is present and the fourth when input P and input Q are present, when input Q is present but not input P and when neither input P nor input Q is present. A further arrangement is described having three variable inputs each linking one of the input legs and seven output windings producing outputs for the following different combinations of energization of the input windings: one or more, any two or more, all three, one and only one, two and only two, one or two, one or three. The number of inputs and core legs can be increased and weighting of the inputs may be effected by arranging the various input windings to embrace predetermined cross-sectional areas of the magnetic core material.