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6-1
CHAPTER
6
Replacement of CPU/Memory Board
Unit (CMU), CPU Module, and DIMM
This chapter explains the procedures for replacing the CPU/memory board unit (CMU), and
for replacing the CPU modules and DIMMs which are mounted on CMU.
■ Section 6.1, “Overview of the CMU” on page 6-1
■ Section 6.2, “Active Replacement and Hot Replacement” on page 6-5
■ Section 6.3, “Cold Replacement” on page 6-16
■ Section 6.4, “CPU Module and DIMM Replacement” on page 6-22
There are three methods for replacing a CMU: active replacement, hot replacement, and cold
replacement. For the definition of each method, see Section 4.1, “Types of Replacement
Procedures” on page 4-2.
Each replacement procedure explains how to replace a CMU. To replace the individual CPU
modules or DIMMs, see also Section 6.4, “CPU Module and DIMM Replacement” on
page 6-22.
Section 6.4, “CPU Module and DIMM Replacement” on page 6-22 also covers the memory
installation conditions when adding more DIMMs.
6.1 Overview of the CMU
This section provides an overview of the CMU and shows CMU mounting locations.
Each CMU has 4 CPU module slots and 32 DIMM slots. When a CMU is replaced, the
mounted parts (CPU modules and DIMMs) must be remounted in the new CMU. These
mounted parts must be remounted at the same locations in the new CMU as their original
pre-swap mounting locations. In addition, the flash memory of each CMU (FMEM) stores
the POST/OpenBoot PROM firmware. The firmware is automatically restored to its pre-swap
version.