Tandem Computers Incorporated

Tandem Computers Inorporated

Mark A Taylor

David J Garcia

Samson K Toy

Paul A Duffy

A pair of substantially identical integrated circuit elements, in the form of microprocessors, are operated in response to the same instruction and data signals that are accessed from a memory by one of the integrated circuits. The accessed instruction and data signal are supplied, via a synchronous interface, to the second integrated circuit, which operates thinking that the supplied data and instruction signals were accessed by it in response to address and control signals. The states of the two integrated circuits are applied to comparator circuitry, both via buffered paths. The comparator circuitry is operated in response to control signals produced by the first integrated circuit to effect comparison on only those signals that are valid at any particular moment in time. Clock-synchronizing circuitry is included to ensure that predetermined state transitions of the clocks used to operate the first and second integrated circuit occur within a prescribed time period.

Real time comparison of integrated circuit operation

A supply voltage monitor for providing an indication of a supply voltage level considered safe for electronic circuit operation includes a supervisory or guard circuit that blocks the output of the monitor in favor of a secondary output for those periods of time when the monitor is considered to not be able of providing a valid reflection of supply voltage status.

Power on system

A digital computer system that contains redundant communication paths between two or more computer components. Each computer component has an interface logic that communicates with other interface logic units to determine if the redundant communication paths are correctly coupled between the components.

Cable connect error detection system

A clock synchronization system includes a clock generator for producing first and second system clock signals that are each received by corresponding ones of a pair of integrated circuits from which the integrated circuits each produce secondary clock signals. The clock system includes synchronizing circuitry that receives the secondary clock signals to determine the phase difference between them, and delaying one of the system clock signals, relative to the other, in a manner that results in the state transitions of the secondary clock signals occur within a period of time of each other.

Clock synchronization system

A regulator circuit supplies a regulated low, DC voltage that is derived from an unregulated voltage provided by a pair of redundant batteries. The regulator circuit comprises regulation control that responds to a feedback signal developed from monitoring the regulated voltage to maintain the regulated voltage at a desired level. Battery monitors supervise the voltage levels of the batteries used, and shut down the regulator when the battery voltages drop below a predetermined voltage level to preserve battery life.

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Cupertino, CA, United States of America

Mark A Taylor