Lenovo 6241, Installation And Service Manual

Page: 67 / 1990

Memory-sparing is supported in both independent memory mode and lockstep memory mode.
The DIMM installation order for memory rank sparing follows the independent mode (performance) or
lockstep mode (RAS) installation order based on the mode of operation selected. For more information, see
“Independent memory mode” on page 53, and “Lockstep memory mode” on page 57.
When you use the memory rank sparing feature, consider the following information:
• Memory rank sparing is not supported if memory mirroring is enabled.
• The spare rank must have identical or larger memory capacity than all the other ranks on the same DDR3
or DDR4 channel.
• When single-rank DIMMs (that is, 4 GB and 8 GB) are used, a minimum of two rank DIMMs must be
installed per memory channel to support memory sparing.
• When multi-rank DIMMs (that is, 16 GB, 32 GB, and 64 GB) are used, one multi-rank DIMM can be
installed per memory channel to support memory sparing.
• The total memory available in the system is reduced by the amount of memory allocated for the spare
ranks.
Independent memory mode
This topic provides information about the independent memory mode and the DIMM installation sequence.
Independent memory mode supports the memory mirroring and memory rank sparing features. When you
use independent memory mode, consider the following. For more information and notes about installing
DIMMs, see “Installing a memory module” on page 46. For more information about DIMM population
sequence, see “Memory mirroring in independent memory mode” on page 54 and “Memory rank sparing in
independent mode” on page 55..
• Independent memory mode provides the most efficient performance.
• You can populate DIMMs in any order and there are no matching requirements. However, the DIMM
population sequence in the following table will provide the best performance when operating in the
supported memory modes.
• When you operate in this mode, the memory channel operates at twice the DDR3 data rate.
• Single-device data correction (SDDC) is supported for x4 SDRAM technology.
The following table lists the installation sequence for independent mode:
Table 10. DIMM population sequence for independent memory mode
DIMM installation order
Independent mode with memory
mirroring disabled Independent mode with memory
mirroring enabled
1 DIMM connector 9 DIMM connectors 9 and 19
2 DIMM connector 6 DIMM connectors 6 and 16
3 DIMM connector 1 DIMM connectors 1 and 15
4 DIMM connector 10 DIMM connectors 10 and 24
5 DIMM connector 15 DIMM connectors 8 and 20
6 DIMM connector 24 DIMM connectors 5 and 17
7 DIMM connector 19 DIMM connectors 2 and 14
8 DIMM connector 16 DIMM connectors 11 and 23
9 DIMM connector 8 DIMM connectors 7 and 21
Chapter 2
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Installing optional devices
53