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B-16 SPARC Enterprise M8000/M9000 Servers Service Manual • June 2010
B.10 Clock Control Unit
A clock control unit (CLKU: formal abbreviation is CLKU_B) is mounted only in the
SPARC Enterprise M9000 server, and it supplies clock signals to a CMU and crossbar
unit (XBU). Furthermore, in the SPARC Enterprise M9000 server with the expansion
cabinet, both CLKUs in the base cabinet and expansion cabinet are connected to
enable each to supply clock signals to the other cabinet.
In the M8000, two LSI chips for clock signals instead of the CLKU are mounted on
the backplane.
FIGURE B-10 shows the CLKU_B.
FIGURE B-10 Clock Control Unit (CLKU_B)
The CLKU has the following characteristics.
■ Only cold replacement is available for CLKU_B.
■ A dedicated LSI chip is used for clock control.
■ CMU and XBU are supplied with the standard clocks, respectively.
■ The CLKU has a label bearing the printed component number and manufacture's
serial number.