Stratus Computer, Inc.

Mark D Tetreault

William Irving Leavitt

Charles J Horvath

Gregory M Green

Peter C Churchill

A digital data processing device includes a bus for transmitting signals (e.g., data and/or address information) between plural functional units (e.g., a central processing unit and a peripheral controller). A first such unit includes first and second processing sections that concurrently apply to the bus complementary portions of like information signals (e.g., longwords containing data). A fault detection element reads the resultant signal from the bus and compares it with at least portions of the corresponding signals originally generated by the processing sections themselves. If there is discrepancy, the fault-detector signals a fault, e.g., causing the unit to be taken off-line. By use of a redundant unit, processing can continue for fault-tolerant operation.

Digital data processing methods and apparatus for fault detection and

A bus device (10) the communicates with other bus devices (12, 13) on a communication channel (14) that includes a plurality of duplicated information buses (16, 17) selectively assumes bus-selection states in which it uses information from one or the other of the buses (16, 17). It also monitors the buses (16, 17) for errors in the information that the buses (16, 17) carry, and it broadcasts an error signal over other lines (18) of the communications channel (14) in response to detection of such an error, but only if an error occurs in information on the bus that its current bus-selection state designates. On the other hand, when an error-broadcast signal indicating an error on either bus in the information transmitted by that device (10) appears on the bus, that bus device (10) retransmits the information, regardless of that device's current bus-selection state. Inconsistent operation phasing among bus devices that have assumed different bus-selection states is thereby avoided.

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Northborough, MA, United States of America

Mark D Tetreault