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Multiprocessor Operational Checks

IP.com Disclosure Number: IPCOM000083495D
Original Publication Date: 1975-Jun-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Bresemann, DH: AUTHOR [+5]

Abstract

In a multiprocessor (MP) system employing a common memory CM a central timer table CT indicates time of last access by various CPU's in the multiprocessor system. If elapsed time since the last CPU update exceeds a threshold M, the corresponding CPU is considered as being faulty; and corrective action is required.

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Multiprocessor Operational Checks

In a multiprocessor (MP) system employing a common memory CM a central timer table CT indicates time of last access by various CPU's in the multiprocessor system. If elapsed time since the last CPU update exceeds a threshold M, the corresponding CPU is considered as being faulty; and corrective action is required.

The CT is periodically asynchronously updated by each of the CPU's, CPU-1 through CPU-N. Within each CPU, a clock drives a counter for measuring elapsed time. When the counter has a count exceeding a predetermined timing threshold, a timing interrupt is sent to the operating system for invoking the CPU multiprocessor check program. This check program first updates the time in the corresponding entry of CT. For example, if CPU-K is CPU-2, then time-2 of CT is updated to the present time.

After the updating, CPU-K then reads all time entries in CT and compares the present time with the time entry for each CPU-J, which is CPU-1 through CPU-N, but not CPU-K. If the difference in time T(now)-T(J) > M, error recovery procedures are invoked. Such procedures are beyond the scope of the present description.

All CPU's have common access to CT such that each and every CPU, through its independently generated timing interrupt, verifies operations of all other CPU's in the MP system. The time-of-day clock can be a common clock, not shown, in the CM or can be generated independently in each CPU, with time- of-day synchronization bein...