David R Barbera, 5917 Old Princeton Rd, Hubbardston, MA 01452

5479648, Dec 26, 1995

Aug 30, 1994

8/297795

David R. Barbera - Worcester MA
Franklin M. Savicki - Sheldonville MA
David E. Splitz - North Attleboro MA

Stratus Computer, Inc. - Marlboro MA

G06F 110
G06F 132

395750

A clock switching circuit switches between clock signals generated by a local clock unit and those generated by a-system clock unit when disabling, and then subsequently enabling, the system clock unit. The clock switching circuit includes a plurality-of switching circuits that are arranged and configured to switch between the system and local clock units so as to provide a substantially uninterrupted stream of clock signals to selected components of a fault-tolerant computer system. This arrangement ensures that information stored on the selected components is not lost during disablement of the system clock unit.

5838899, Nov 17, 1998

Jun 5, 1996

8/658563

William I. Leavitt - Lexington MA
Conrad R. Clemson - Shrewsbury MA
Jeffrey S. Somers - Northboro MA
John M. Chaves - Hudson MA
David R. Barbera - Worcester MA
Shawn A. Clayton - Worcester MA

Stratus Computer - Marlboro MA

G06F 1100

39518509

A fault-isolating digital data processing apparatus includes plural functional units that are interconnected for point-to-point communications by a plurality of buses. The functional units monitor the buses to which they are attached and signal the other units in the event there are bus communication errors. The functional units can simultaneously enter into an error isolation phase, e. g. , in response to a bus error signaled by one of the units. During this phase, each unit transmits test data (e. g. , predetermined patterns of O's and 1's) onto at least one of its attached buses. The functional units continue to monitor the buses and to signal bus errors while the test data is being transmitted. In addition to signaling bus errors, the functional units can signal unit-level (or "board") faults when they detect fault in their own operation. To this end, each unit includes error isolation functionality that signals a fault based on (i) whether that unit signaled a loopback error with respect to its own operation; (ii) whether that unit or another unit signaled a bus error during the error isolation phase; and/or (iii) whether any other functional unit signaled that it was faulty during the error isolation phase.