Patent GB-926015-A (GB)
Title: Superconductive binary adder
IPC: G06F7/38
Filed: 1959-08-18
Abstract: 926,015. Superconductive circuits. INTERNATIONAL BUSINESS MACHINES CORPORATION. Aug. 18, 1959 [Nov. 18, 1958], No. 28206/59. Class 40 (9). [Also in Group XIX] A parallel feed is used in an adder for three binary digits. Three digits to be added are signalled by trigger units T numbered 10, 11, 12, the strength of each signal being 8 units. Three pairs of cryotrons K1, K2, K3, K4 and K5, K6 are so arranged that the gate of one member of a pair is -resistive when the other is conductive. The cryotron pairs are fed by current sources 20 (16 units), 22 (8 units) and 28 (8 units) and all the current from each source flows through only one gate of a pair. Cryotrons K1, K2, K3, K4 go resistive at a critical current between 8 and 16 units and cryotrons K5, K6 have critical currents of 20 units. Cryotrons K3, K4 are slaves of K1, K2 and give a carry " 1 " signal on terminal C if the sum is 2 or 3 and give a carry " 0 " signal at terminal C if the sum is 1. Circuits from the trigger units and from source 20 join at points 24, 26 to control cryotrons K5, K6 which give the sum on terminals S, S. In a modification (Fig. 2, not shown) all the cryotrons have the same critical current of 10 units, cryotrons K5, K6 each being shunted so that a total current of 20 units is necessary to drive it resistive. Cross-connected cryotrons are connected in the two branches of the circuit fed by source 20 to stabilize the condition of the circuit. Trigger circuits T, TT, Fig. 3.-A trigger circuit T gives an output signal " 1 " or " 0 " under the control of the setting windings of K11, K12. Two parallel circuits connected to source 50 include the cross-connected gates and control windings of cryotrons K13, K14, the gates of setting cryotrons K11, K12 and the control windings of cryotrons K15, K16. Current source 54 provides the output under the control of K15, K16. Additional cryotron K17, K18 may be used to control a second output from current source 56 in a trigger TT. The two outputs may be of different current strength. Modified adders.-Each two-level trigger TT, Fig. 4, gives a signal strength of 16 units to the right and 8 units to the left. The outputs of strength 8 units are connected direct to points 24b and 26b where they join with currents from source 20b. Each cryotron has a critical current of 20 units. Fig. 5 shows bi-stable input trigger circuits 80, 82, and 84 inductively linked to a carry output trigger 90 by closed loops L90c, L90d and linked to a sum output trigger 100 by closed loops L100c, L100d. A single battery 70 feeds all the trigger circuits in series with 20 units of current. The loops are always superconducting and normally carry no current. All the cryotrons in this embodiment have a critical current of 10 units. When 20 units flow in arm 80d of trigger 80 to register "0," 6 units flow in loop L90c and continue to flow until the current in arm 80d is stopped. Similarly "0 " signals set in triggers 80, 82, 84 are accompanied by 4 units of current in loop L100c and " 1 " signal in triggers 80, 82, 84 are accompanied by 6 units of current in loop L90d and 4 units of current in loop 100d. The carry output trigger circuit 90 also feeds one of the loops L100c, L100d with 8 units of current in accordance with the setting of the trigger. Resistive gates in pairs of cryotrons K110S, K100S and K90C, K90#C indicate the sum and the carry outputs.