Memory Rank Sparing - IBM System x3550 M4 Installation And User Manual

v When you use memory mirrored channel, you must install a pair of DIMMs at a
v The maximum available memory is reduced to half of the installed memory when
v For UDIMMs, DIMM connectors 3, 6, 7, and 10 for microprocessor 1 and DIMM
The following diagram lists the DIMM connectors on each memory channel.
Figure 1. Connectors on each memory channel
The following table shows the installation sequence for memory mirrored channel
mode:

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 either rank sparing memory or memory mirrored channel in the
Setup utility (see "Starting the Setup utility" on page 109). When you use the
memory rank sparing feature, consider the following information:
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.
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.
connectors 15, 18, 19, and 22 for microprocessor 2 are not used in memory
mirrored channel mode.
Table 8. 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
Note: 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.
Number of installed
microprocessor
1
1
1
1
1
1
2
2
2
2
2
2
Chapter 2. Installing optional devices
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
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