IBM X3950 X5 Problem Determination And Service Manual page 204

Types 7145, 7146, 7143, and 7191

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v A minimum of two DIMMs must be installed in the memory expansion module

v The maximum operating speed of the memory expansion module is determined

v The memory expansion module does not come with any DIMMs installed when

v The server supports non-mirroring mode and memory-mirroring mode.

IBM System x3850 X5 and x3950 X5 Types 7145, 7146, 7143, and 7191: Problem Determination and Service Guide

for each microprocessor in the host server.

by the slowest DIMM installed in the memory expansion module.

you purchase it as a option. When you install DIMMs, install them in the order

shown in the following tables to optimize system performance.

– Non-mirroring mode. When you use the non-mirroring mode, install DIMMs

as indicated in the following table.

Table 23. Non-mirroring mode DIMM population sequence for the memory expansion

Pairs of DIMMs

Note: When you populate DIMMs in the memory expansion module,

populate the larger capacity DIMMs first, then the smaller capacity DIMMs.

– Memory-mirroring mode. When you use the mirroring mode feature,

consider the following information:

- Memory-mirroring mode replicates and stores data on sets of four DIMMs

simultaneously. If a failure occurs, the memory controller switches from the

primary set of memory DIMMs to the backup set of DIMMs. To enable

memory mirroring through the Setup utility, select System Settings →

Memory. For more information, see "Configuring the server" on page 202.

- DIMMs must be installed in sets of four. The DIMMs in each set must be

the same size and type. This is applicable also when the memory expansion

module is attached to a host server and the host server has an optional

memory tray installed in the server. You must install DIMMs in sets of four

DIMMs for memory-mirroring mode in each (server, memory tray, and the

memory expansion module).

- The maximum available memory is reduced to half of the installed memory

when memory mirroring is enabled. For example, if the memory expansion

DIMM connector population sequence

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