Memory Mirrored Channel - Lenovo System x3500 M4 Installation And Service Manual

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.
You can enable memory mirrored in the Setup utility (see "Starting the Setup utility" on page 107).
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 is
enabled. For example, if you install 64 GB of memory using RDIMMs, only 32 GB of addressable memory
is available when you use memory mirrored channel.
The following diagram lists the DIMM connectors on each memory channel.
Microprocessor 2
Microprocessor 1
Figure 42. Connectors on each memory channel
Note: You can install DIMMs for microprocessor 2 as soon as you install microprocessor 2; you do not have
to wait until all of the DIMM connectors for microprocessor 1 are filled.
The following table shows the installation sequence for memory mirrored mode:
Table 6. Memory mirrored channel mode DIMM population sequence
Number of DIMMs
First pair of DIMMs
Second pair of DIMMs
Third pair of DIMMs
Fourth pair of DIMMs
Fifth pair of DIMMs
Sixth pair of DIMMs
64
System x3500 M4 Installation and Service Guide
Channel
Channel
Number of installed
microprocessor
1
1
1
1
1
1
DIMM connector
1, 4
9, 12
2, 5
8, 11
7, 10
3, 6