Excavating
Patent
1991-02-20
1993-08-24
LaRoche, Eugene R.
Excavating
371 471, 371 61, G06F 1100
Patent
active
052396410
ABSTRACT:
A method and apparatus for synchronizing a plurality of processors. Each processor runs off of its own independent clock, indicates the occurrence of a prescribed process or event on one line and receives signals on another line for initiating a processor wait state. Each processor has a counter which counts the number of processor events indicated since the last time the processors were synchronized. When an event requiring synchronization is detected by a sync logic circuit associated with the processor, the sync logic circuit generates the wait signal after the next processor event. A compare circuit associated with each processor then tests the other event counters in the system and determines whether its associated processor is behind the others. If so, the sync logic circuit removes the wait signal until the next processor event. The processor is finally stopped when its event counter matches the event counter for the fastest processor. At that time, all processors are synchronized and may be restarted for servicing the event. If no synchronizing event occurs before an event counter reaches its maximum value, and overflow of the event counter forces resynchronization. A cycle counter is provided for counting the number of clock cycles since the last processor event. The cycle counter is set to overflow and force resynchronization at a point before maximum interrupt latency time is exceeded.
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Glenbocki Christopher R.
LaRoche Eugene R.
Tandem Computers Incorporated
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