Digital systems and hardware/firmware algorithms
Digital systems and hardware/firmware algorithms
Coordination of time-of-day clocks among multiple systems
IBM Journal of Research and Development
Reliability, availability, and serviceability (RAS) of the IBM eServer z990
IBM Journal of Research and Development
RAS strategy for IBM S/390 G5 and G6
IBM Journal of Research and Development
System control structure of the IBM eServer z900
IBM Journal of Research and Development
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This paper describes a fully redundant clock generation and distribution approach with a fully dynamic switchover capability and concurrent repair. It highlights the challenges as the design evolved from a single source, to a "cold" standby backup, and finally to a fully redundant transparent switchover with no interruption of the workloads running on an IBM System z9TM. The function split between hardware and the various levels of firmware is described, including the methods to determine the defect component in the clock distribution paths. Finally, we describe the joint effort with a major chip technology vendor to design and develop the necessary circuitry, according to the z9TM requirements, for clock synchronization and switching.