Abstract: An output driver circuit comprises a plurality of parallel pull up and pull down circuits each comprising at least one transistor switch switchable between on and off states and circuitry operable to maintain a desired resistance in the circuit when the transistor switch is switched on, and switch actuating circuitry including time delay circuitry for effecting a sequence of transistor switching operations in said pull-up and pull-down circuits with a time delay between successive operations, each operation effecting simultaneous switching of a transistor in one pull-up circuit and one pull-down circuit, whereby the output impedance is stabilised during a change in signal on the output terminal.

Abstract: Computer appratus includes an instruction execution unit (13) having a plurality of functional units (14,16) each arranged to execute at least part of an instruction and instruction issuing circuitry (10,12) for issuing simultaneously a group of separate compatible instructions to the execution unit (13) the circuitry (12) having means for classifying each instruction in dependence on the or each functional unit required for execution of that instruction and means for testing the classification of successive instructions and selecting a group which according to their classification are compatible for simultaneous issue to the execution unit (13) without conflicting demands on any function unit (14,16) in the execution unit.

Abstract: A digital memory is configured as a hierarchical system with at least three levels. The first level consists of a main bus and interfacing for one or more main memory units; the second level consists of a separate second level bus in each main memory unit with a plurality of memory frames independently interfaced to each bus; and the third level consists of a separate third level bus in each memory frame with a plurality of memory storage blocks independently interfaced to each bus. Virtual addressing is employed in which the whole of each address is decoded in the individual memory block which includes for the purpose soft-ware settable registers containing identification numbers.

Abstract: In a binary parallel complementing L.S.I. adder, a C-MOS transmission gate is provided in each stage with its input and output directly connected to the carry in and carry out leads of the stage. The gate is switched by complementary control bits derived by stage input logic operating on the bits to be summed, whereby very fast passage of a carry through the stages is achieved. The transmission gate consists of p- and n- channel MOS transistors with their sources connected in common to the input and their drain electrodes likewise connected in common to the output.