David R Barbera

US Patent:

54796482, Dec 26, 1995

Filed:

Aug 30, 1994

Appl. No.:

8/297795

Inventors:

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

Assignee:

Stratus Computer, Inc. - Marlboro MA

International Classification:

G06F 110
G06F 132

US Classification:

395750

Abstract:

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.

US Patent:

58388990, Nov 17, 1998

Filed:

Jun 5, 1996

Appl. No.:

8/658563

Inventors:

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

Assignee:

Stratus Computer - Marlboro MA

International Classification:

G06F 1100

US Classification:

39518509

Abstract:

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.