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16-1
CHAPTER
16
Clock Control Unit Replacement
This chapter explains the replacement procedure for the clock control unit (CLKU).
It covers the following:
■ Section 16.1, “Overview of the CLKU” on page 16-1
■ Section 16.2, “Cold Replacement” on page 16-4
Cold replacement is the only swapping method that can be used for the CLKU. For
the definition of the swapping method, see Section 4.1, “Types of Replacement
Procedures” on page 4-2.
16.1 Overview of the CLKU
This section provides an overview of the CLKU and describes its mounting
locations.
The CLKU is mounted only in the M9000, and it supplies clock signals to CPU
memory board units (CMUs) and crossbar units (XBUs). CLKUs are duplicated, but
active maintenance cannot be performed on them. For the M9000 with the expansion
cabinet, there are cables available for connecting the clocks in the base cabinet to
those in the extension cabinet.
FIGURE 16-1 and FIGURE 16-2 show the CKLU mounting locations in the cabinets of the
M9000 (base cabinet) and M9000 (with the expansion cabinet), respectively.