Lenovo System x3550 M4 Installation And Service Manual page 235

• 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.
Ch2 Ch3
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
First pair of DIMMs
Second pair of DIMMs
Third pair of DIMMs
Fourth pair of DIMMs
Fifth pair of DIMMs
Sixth pair of DIMMs
Seventh pair of DIMMs
Eighth pair of DIMMs
Ninth pair of DIMMs
Tenth pair of DIMMs
Eleventh pair of DIMMs
Twelfth pair of DIMMs
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 95.
The maximum available memory is reduced when memory rank sparing mode is enabled.
The following diagram lists the DIMM connectors on each memory channel.
Ch1 Ch0 Ch2 Ch3
Number of installed
microprocessor
1
1
1
1
1
1
2
2
2
2
2
2
Ch1 Ch0
DIMM connector
1, 4
9, 12
2, 5
8, 11
3, 6
7, 10
13, 16
21, 24
14, 17
20, 23
15, 18
19, 22
.
Chapter 6 Removing and replacing components
221