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• The maximum available memory is reduced to half of the installed memory when memory mirrored
channel is enabled. For example, if you install 64 GB of memory using RDIMMs, only 32 GB of
addressable memory is available when you use memory mirrored channel.
• For UDIMMs, DIMM connectors 3, 6, 7, and 10 for microprocessor 1 and DIMM connectors 15, 18, 19,
and 22 for microprocessor 2 are not used in memory mirrored channel mode.
The following diagram lists the DIMM connectors on each memory channel.
Figure 138. Connectors on each memory channel
The following table shows the installation sequence for memory mirrored channel mode:
Table 22. Memory mirrored channel mode DIMM population sequence
Number of DIMMs
Number of installed
microprocessor
DIMM connector
First pair of DIMMs
1
1, 4
Second pair of DIMMs
1
9, 12
Third pair of DIMMs
1
2, 5
Fourth pair of DIMMs
1
8, 11
Fifth pair of DIMMs
1
3, 6
Sixth pair of DIMMs
1
7, 10
Seventh pair of DIMMs
2
13, 16
Eighth pair of DIMMs
2
21, 24
Ninth pair of DIMMs
2
14, 17
Tenth pair of DIMMs
2
20, 23
Eleventh pair of DIMMs
2
15, 18
Twelfth pair of DIMMs
2
19, 22
DIMM connectors 3, 6, 7, 10, 15, 18, 19, and 22 are not used in memory mirrored channel mode when UDIMMs
are installed in the server.
Memory rank sparing
The memory rank sparing feature disables the failed memory from the system configuration and activates a
rank sparing DIMM to replace the failed active DIMM.
You can enable rank sparing memory in the Setup utility, select
System Settings
➙
Memory
. For more
information, see “Using the Setup utility” on page 97.
The maximum available memory is reduced when memory rank sparing mode is enabled.
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System x3550 M4 Installation and Service Guide
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