| 摘要 |
A method and apparatus for specifying offsets from an external time reference (ETR) for selected logical partitions of a partitioned information handling system. Each logical partition has a logical time-of-day (TOD) clock which may be set independently of the host system clock by specifying an epoch offset from the host clock. A system operator is presented with a display panel in which the operator may specify the magnitude and sign of an ETR offset for each logical partition selected to have an ETR offset. Each logical partition, upon being activated, issues a Store Clock (STCK) instruction to read its own logical TOD clock as well as a Store ETR (STETR) instruction to read the ETR. If the logical partition has a specified ETR offset, the logical partition manager simulates the STETR instruction by adding or subtracting the ETR offset to the real ETR time and returning the modified value to the partition; otherwise, the logical partition manager returns the real ETR time to the partition. If the read ETR time (as returned by the STETR instruction) differs from the read logical clock time, the logical partition issues a Set Clock (SCK) instruction to reset the logical partition clock to the ETR time. The logical partition manager simulates this latter instruction by computing the difference between the two times and storing the difference in an epoch offset field for the partition. The invention permits sets of logical partitions to be synchronized to different clock values, either for test purposes or operation in different time zones.
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