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Online-Spare Memory - IBM 7945G2U Installation And User Manual

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The following table lists the installation sequence for installing DIMMs in
memory-mirroring mode.
When you install or remove DIMMs, the server configuration information changes.
When you restart the server, the system displays a message that indicates that the
memory configuration has changed.

Online-spare memory

The server supports online-spare memory. This feature disables the failed memory
from the system configuration and activates an online-spare DIMM to replace the
failed active DIMM. You can enable either online-spare memory or memory
mirroring in the Setup utility (see "Using the Setup utility" on page 144). When you
use the memory online-spare feature, consider the following information:
v The memory online-spare feature is supported on server models with an Intel
v When you enable the memory online-spare feature, you must install three DIMMs
v The maximum available memory is reduced to 2/3 of the installed memory when
The following table shows the installation sequence for installing DIMMs for each
microprocessor and the online-spare DIMM in memory online-spare mode:
Table 10. Memory-mirroring mode DIMM population sequence
First pair of DIMMs
Second pair of DIMMs
Third pair of DIMMs
Fourth pair of DIMMs
Fifth pair of DIMMs
Sixth pair of DIMMs
Note: DIMM connectors 7, 8, 9, 16, 17, and 18 are not used in memory-mirroring mode.
5600 series microprocessor.
per microprocessor at a time. The first DIMM must be in channel 0, the second
DIMM in channel 1, and the online-spare DIMM in channel 2. The DIMMs must
be identical in size, type, rank, and organization, but not in speed. The channels
run at the speed of the slowest DIMM in any of the channels.
memory online-spare mode is enabled. For example, if you install 72 GB of
memory using RDIMMs, only 48 GB of addressable memory is available when
you use memory online-spare.
Table 11. Memory online-spare mode DIMM population sequence
Microprocessor 1
Microprocessor 2
Number of installed
DIMM connector
3, 6, 9
3, 6, 9, 2, 5, 8
3, 6, 9, 2, 5, 8, 1, 4, 7
12, 15, 18,
12, 15, 18, 11, 14, 17,
12, 15, 18, 11, 14, 17, 10, 13, 16
DIMM connector
3, 6
2, 5
1, 4
12, 15
11, 14
10, 13
Chapter 2. Installing optional devices



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