Electrical computers and digital processing systems: support – Clock – pulse – or timing signal generation or analysis
Reexamination Certificate
2011-04-05
2011-04-05
Lee, Thomas (Department: 2115)
Electrical computers and digital processing systems: support
Clock, pulse, or timing signal generation or analysis
C713S400000, C713S600000, C718S001000
Reexamination Certificate
active
07921319
ABSTRACT:
A method and system for providing a virtual clock on a computer by multiplying the number of instructions executed by the average instruction execution time. It is however not reliable to use this generic computation for virtualization of application in a fault tolerant system because the virtual clock computed like this quickly deviates from the system clock. A virtual clock computation is provided which includes periodic readjustment of the virtual to the system clock. Also, the errors coming from rounding of the number of executing instruction are suppressed.Taking the assumption that the user instruction counters are maintained synchronized in the operational and the replication computers, replacing the system clock access by a virtual clock when virtualizing applications thus turning the system clock acquisition into a deterministic event. Replicating the system clock access can be thus done by re-executing the application code in the replication machine avoiding transfer of information at each system clock access of the virtualized application programs.
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patent: 2004/0205372 (2004-10-01), Moser et al.
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Bergheaud Philippe
Vertes Marc Philippe
Abbaszadeh Jaweed A
International Business Machines - Corporation
Lee Thomas
Mims Jr. David A.
Yee & Associates P.C.
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