IBM 71453RU manual Pairs of DIMMs Dimm connector population sequence

vA minimum of two DIMMs must be installed in the memory expansion module for each microprocessor in the host server.

vThe maximum operating speed of the memory expansion module is determined by the slowest DIMM installed in the memory expansion module.

vThe memory expansion module does not come with any DIMMs when you purchase it as an optional device. When you install DIMMs, install them in the order shown in the following tables to optimize system performance.

vThe memory expansion module supports non-mirroring mode and memory-mirroring mode through the host server.

–Non-mirroring mode. When you use the non-mirroring mode, install DIMMs as indicated in the following table.

Table 12. Non-mirroring mode DIMM population sequence for the memory expansion module

Pairs of DIMMs	DIMM connector population sequence
Pair 1	28, 29
Pair 2	9, 16
Pair 3	1, 8
Pair 4	20, 21
Pair 5	26, 31
Pair 6	11, 14
Pair 7	3, 6
Pair 8	18, 23
Pair 9	27, 30
Pair 10	10, 15
Pair 11	2, 7
Pair 12	19, 22
Pair 13	25, 32
Pair 14	12, 13
Pair 15	4, 5
Pair 16	17, 24

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 DIMMs simultaneously. If a failure occurs, the memory controller switches from the primary set of DIMMs to the backup set of DIMMs. To enable memory mirroring through the Setup utility, select System Settings → Memory. For more information, see “Using the Setup utility” on page 96.

-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).

Chapter 2. Installing optional devices 85