IBM NeXtScale nx360 M4 Installation And Service Manual page 155

Table 18. Normal mode DIMM installation sequence
Number of installed
microprocessor
One microprocessor
installed
Two microprocessors
installed
Memory mirrored channel
Memory mirrored channel mode replicates and stores data on two pairs of DIMMs
within two channels simultaneously.
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 25. When you use the memory
mirrored channel feature, consider the following information:
v 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.
v 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 19. Memory mirrored channel mode DIMM population sequence
Number of installed
microprocessor
One microprocessor
installed
Two microprocessors
installed
Replacing a memory module
Use this information to install a DIMM.
1. Read the safety information that begins on "Safety" on page vii and
"Installation guidelines" on page 93.
2. Turn off the server and peripheral devices and disconnect the power cords
and all external cables, if necessary.
3. Remove the cover (see "Removing the compute node cover" on page 110).
4. Remove the air baffle (see "Removing the air baffle" on page 113).
5. Carefully open the retaining clips on each end of the DIMM connector and
remove the DIMM.
Attention: To avoid breaking the retaining clips or damaging the DIMM
connectors, open and close the clips gently.
DIMM connector population sequence
4, 3, 1, 2
4, 5, 3, 6, 1, 8, 2, 7
DIMM connector population sequence
4, 3, 1, 2
4, 3, 5, 6, 1, 2, 8, 7
Chapter 5. Removing and replacing components
137