114 Installing System Components
System Memory
You can upgrade your system memory to a maximum of 128 GB by installing
667-MHz registered parity DDR2 memory modules (DIMMs) in sets of
512-MB, 1-GB, 2-GB, 4-GB, or 8-GB single- or dual-ranked modules (quad-
ranked modules are not supported). The memory sockets are located on the
system board under the memory module cooling shrouds and are split into
two separate groups of eight sockets each. Each eight-socket group is adjacent
to its respective processor.
Your system hardware supports Non-Uniform Memory Architecture (NUMA).
Each processor has its own memory controller and local memory for reduced
access times, but it can also access memory from another processor. This
architecture improves system performance if an operating system is installed
that supports this feature.
NOTICE: To enable NUMA, run the System Setup program and disable the Node
Interleaving option. See "Using the System Setup Program" on page47.

General Memory Module Installation Guidelines

To ensure optimal performance of your system, observe the following
guidelines when configuring your system memory.
• Memory must be installed in configurations of four, eight, or sixteen
DIMMs. The minimum configuration is four 512-MB DIMMs.
•DIMMs m
ust be installed in matched sets of
identical speed, technology,
and size in the following sockets:
– A1, A2, B1, and B2 — four identical DIMMs in this set
– A3, A4, B3, and B4 — four identical DIMMs in this set
– A5 through A8 and B5 through B8 — eight identical DIMMs in this
set
• Minimum configurations (four DIMMs) must occupy sockets A1, A2, B1,
and B2.
• A matched DIMM set can be mixed with another matched DIMM set of
the next smaller size. For example, a DIMM set containing 2-GB DIMMs
can be mixed with another DIMM set containing 1-GB DIMMs, but not a
set containing 512-MB DIMMs. The larger capacity DIMMs must occupy
the lower-numbered DIMM sockets.