Lenovo System x3550 M4 Installation And Service Manual page 234

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Figure 137. DIMM connectors location
DIMM installation sequence
Depending on the server model, the server may come with a minimum of one 2 GB or 4 GB DIMM installed in
slot 1. When you install additional DIMMs, install them in the order shown in the following table to optimize
system performance.
In general, all three channels on the memory interface for each microprocessor can be populated in any
order and have no matching requirements.
Table 21. Normal mode DIMM installation sequence
Number of installed
microprocessor
One microprocessor installed
Two microprocessors installed
Memory mirrored channel
Memory mirrored channel mode replicates and stores data on two pairs of DIMMs within two channels
simultaneously.
If a failure occurs, the memory controller switches from the primary pair of memory DIMMs to the backup
pair of DIMMs. To enable memory mirrored channel through the Setup utility, select System Settings ➙
Memory. For more information, see "Using the Setup utility" on page 95. When you use the memory mirrored
channel feature, consider the following information:
• When you use memory mirrored channel, you must install a pair of DIMMs at a time. The two DIMMs in
each pair must be identical in size, type, and rank (single, dual, or quad), and organization, but not in
speed. The channels run at the speed of the slowest DIMM in any of the channels.
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Lenovo System x3550 M4 Installation and Service Guide
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Ch1 Ch0
DIMM connector population sequence
1, 4, 9, 12, 2, 5, 8, 11, 3, 6, 7, 10
1, 13, 4, 16, 9, 21, 12, 24, 2, 14, 5, 17, 8, 20, 11, 23, 3, 15, 6, 18, 7, 19, 10, 22
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