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17-1
CHAPTER
17
Crossbar Unit Replacement
This chapter explains the replacement procedure for crossbar units (XBUs). It covers
the following:
■ Section 17.1, “Overview of XBUs” on page 17-1
■ Section 17.2, “Cold Replacement” on page 17-4
As a replacement method for XBUs, only the cold replacement method can be used.
For the definition of the replacement method, see Section 4.1, “Types of Replacement
Procedures” on page 4-2.
17.1 Overview of XBUs
This section provides an overview of XBUs and describes their mounting locations.
XBUs are mounted only in the M9000. XBUs logically switch between connections to
CPU memory board units (CMUs) and I/O units (IOUs). Active maintenance cannot
be performed on XBUs even during degraded operation involving the XBUs.
FIGURE 17-1 and FIGURE 17-2 show the mounting locations of XBUs in the cabinets of
the M9000 (base cabinet), and M9000 (with the expansion cabinet), respectively.