Lenovo NeXtScale nx360 M5, Installation And Service Manual, Page: 173 / 1022

• Install even number of DIMMs for single-rank or dual-rank.
Table 12. Memory rank sparing mode DIMM population sequence when only quad-rank RDIMMs are installed
Number of installed
microprocessor
DIMM connector population sequence on the system board
One microprocessor installed
7, 8-> 1, 2-> 5, 6-> 3, 4
Two microprocessors installed 7, 8-> 9, 10-> 1, 2-> 15, 16-> 5, 6-> 11, 12-> 3, 4-> 13, 14
Memory mirrored channel
Memory mirrored channel mode replicates and stores data on two pairs of DIMMs within two channels
simultaneously.
In memory mirrored channel mode, the memory contents are mirrored between Channel 0 and Channel 1
and also between Channel 2 and Channel 3. As a result of the mirroring, the total physical memory available
to the system is half of what is populated. Mirrored channel mode requires that Channel 0 and Channel 1,
and Channel 2 and Channel 3 must be populated identically with regards to size and organization. DIMM slot
populations within a channel do not have to be identical but the same DIMM slot location across Channel 0
and Channel 1 and across Channel 2 and Channel 3 must be populated the same.
If a failure occurs, the memory controller switches from the primary pair of memory DIMMs to the backup
pair of DIMMs. To enable memory mirrored channel through the Setup utility, select
System Settings ➙
Memory . For more information, see “Using the Setup utility” on page 32. When you use the memory
mirrored channel feature, consider the following information:
• When you use memory mirrored channel, you must install a pair of DIMMs at a 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.
• The maximum available memory is reduced to half of the installed memory when memory mirrored
channel is enabled. For example, if you install 8 GB of memory using RDIMMs, only 4 GB of addressable
memory is available when you use memory mirrored channel.
The following table shows the installation sequence for memory mirrored channel mode:
Table 13. Memory mirrored channel mode DIMM population sequence
Number of installed
microprocessor
DIMM connector population sequence
One microprocessor installed 6, 8-> 1, 3-> 5, 7-> 2, 4
Two microprocessors installed 6, 8-> 9, 11-> 1, 3-> 14, 16-> 5, 7-> 10, 12-> 2, 4-> 13, 15
Replacing a memory module
Use this information to install a DIMM.
Before you install a dual inline memory module (DIMM), complete the following steps:
1. Read “Safety” on page v and “Installation guidelines” on page 101.
2. If the compute node is installed in a NeXtScale n1200 Enclosure, remove it (see “Removing a compute
node from a chassis” on page 104 for instructions).
3. Carefully lay the compute node on a flat, static-protective surface, orienting the compute node with
the bezel pointing toward you.
Step 1. Remove the cover (see “Removing the compute node cover” on page 113).
Chapter 5
.
Removing and replacing components
159