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Browse Prior Art Database

Primary Clock Synchronization Facility

IP.com Disclosure Number: IPCOM000122068D
Original Publication Date: 1991-Oct-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 40K

Publishing Venue

IBM

Related People

Smith Sr, RM: AUTHOR [+3]

Abstract

This article describes an improvement in synchronization multiple Time-of-Day (TOD) clocks in a tightly coupled multiprocessing system. This invention uses the on-time-event (OTE) of a particular TOD clock as the common OTE to start all stopped TOD clocks and to determine whether clocks are running in synchronism. An OTE occurs every 1.048576 seconds and corresponds to a carry out of bit position 32 of a TOD clock.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

Primary Clock Synchronization Facility

      This article describes an improvement in synchronization
multiple Time-of-Day (TOD) clocks in a tightly coupled
multiprocessing system.  This invention uses the on-time-event (OTE)
of a particular TOD clock as the common OTE to start all stopped TOD
clocks and to determine whether clocks are running in synchronism.
An OTE occurs every 1.048576 seconds and corresponds to a carry out
of bit position 32 of a TOD clock.

      Each TOD clock in the system has a unique clock ID associated
with it.  A global register, called the primary-clock-selection
register (PCSR) is provided.  The contents of the register specify a
TOD clock as the primary TOD clock and can be set and read by each
CPU in the system. The carry out of bit 32 of the primary TOD clock
is the common OTE for all TOD clocks in the system.  The common OTE
is compared with the OTE of a TOD clock to determine if the clock is
running in synchronism with the primary TOD clock. If they are not
running in synchronism, a sync check is reported to the CPU accessing
the TOD clock.  Any TOD clock in the system can be designated by the
program as the primary TOD clock.  The figure illustrates how the
common OTE is used to detect sync check conditions.

      Disclosed anonymously.