Dimm Installation Sequence; Memory Mirrored Channel - IBM 7383 Installation And Service Manual

DIMM installation sequence

Depending on the server model, the server may come with a minimum of one 2
GB or 4 GB DIMM installed in slot 1. When you install additional DIMMs, install
them in the order shown in the following table to optimize system performance.
In general, all three channels on the memory interface for each microprocessor can
be populated in any order and have no matching requirements.
Table 5. Independent 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.
You can enable memory mirrored in the Setup utility (see "Starting the Setup
utility" on page 106).
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
v The maximum available memory is reduced to half of the installed memory
The following diagram lists the DIMM connectors on each memory channel.
Figure 25. Connectors on each memory channel
DIMM connector population sequence
1, 4, 9, 12, 2, 5, 8, 11, 10, 7, 6, 3
1, 13, 4, 16, 9, 21, 12, 24, 2, 14, 5, 17, 8, 20, 11, 23, 22, 10, 19, 7, 18, 6, 15, 3
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.
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.
Chapter 2. Installing optional devices
63