Memory Mirroring In Lockstep Mode - IBM System x3850 X6 Installation And Service Manual

The following table lists the DIMM installation sequence for lockstep memory
mode:

Memory mirroring in lockstep mode

Use this information for notes and details about using the memory mirroring
feature in lockstep memory mode.
Memory-mirroring replicates and stores data on DIMMs across all four memory
channels for the compute book and DDR3 channels simultaneously. If a failure
occurs, the memory controller switches from the DIMMs on the primary channels
to the DIMMs on the backup channels.
To enable memory mirroring through the Setup utility, select System Settings →
Memory → Memory Mode. For more information, see "Using the Setup utility" on
page 126. For more information and notes about installing DIMMs, see "Installing
a memory module" on page 47 and "Lockstep memory mode" on page 59.
Consider the following information when using the memory mirroring feature in
lockstep memory mode:
v The compute book memory channel 0 mirrors memory channel 1, and memory
v DIMMs must be installed across the memory channels for each compute book
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System x3850 X6 and x3950 X6 Types 3837 and 3839: Installation and Service Guide
Table 15. DIMM population sequence for lockstep memory mode
DIMM installation order
1
2
3
4
5
6
7
8
9
10
11
12
channel 2 mirrors memory channel 3. This mirroring provides redundancy in
memory but reduces the total memory capacity in half.
when using the memory mirroring feature in lockstep mode.
Lockstep mode with
memory mirroring disabled
DIMM connectors 9 and 15
DIMM connectors 6 and 24
DIMM connectors 1 and 19
DIMM connectors 10 and 16
DIMM connectors 8 and 14
DIMM connectors 5 and 23
DIMM connectors 2 and 20
DIMM connectors 11 and 17
DIMM connectors 7 and 13
DIMM connectors 4 and 22
DIMM connectors 3 and 21
DIMM connectors 12 and 18
Lockstep mode with
memory mirroring enabled
DIMM connectors 1 and 9,
and DIMM connectors 15
and 19
DIMM connectors 6 and 10,
and DIMM connectors 16
and 24
DIMM connectors 2 and 8,
and DIMM connectors 14
and 20
DIMM connectors 5 and 11,
and DIMM connectors 17
and 23
DIMM connectors 3 and 7,
and DIMM connectors 13
and 21
DIMM connectors 4 and 12,
and DIMM connectors 18
and 22