Patent
1996-06-28
1998-09-08
Heckler, Thomas M.
G06F 112
Patent
active
058058702
ABSTRACT:
Each processor in a multiprocessor system has a local clock. Variables "TIME.sub.-- DELTA" and "TIME.sub.-- PREV", are defined for each processor and maintained in databases. TIME.sub.-- DELTA is decremented or incremented to zero, dependent upon whether a positive or negative time delta is specified by the user, and is modified at each clock tick. TIME.sub.-- PREV represents the time to bring the current processor up to the remaining processors' time. A user-specified time adjustment causes an ADJTIME system call. When a second ADJTIME call is subsequently made responsive to a next adjustment, the system examines each processor's TIME.sub.-- DELTA and determines which processor has advanced the furthest and calculates the time for each processor to catch up with this most-advanced processor. This time value is thereafter stored in the TIME.sub.-- PREV field and applied at the next system clock tick. Finally, the ADJTIME call updates each processor's TIME.sub.-- DELTA with the new value as specified by the user. Updates to the clock are thus maintained on a per clock tick basis.
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patent: 5041966 (1991-08-01), Nakai et al.
patent: 5131084 (1992-07-01), Kasashima et al.
patent: 5228138 (1993-07-01), Pratt et al.
patent: 5392421 (1995-02-01), Lennartsson
patent: 5572554 (1996-11-01), Heflin
Carwell Robert M.
Heckler Thomas M.
International Business Machines - Corporation
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