IBM 79463AU Installation And User Manual page 69

Note: To determine the type of a DIMM, see the label on the DIMM. The
information on the label is in the format xxxxx nRxxx PC3-xxxxx-xx-xx-xxx.
The numeral in the sixth numerical position indicates whether the DIMM is
single-rank (n=1) or dual-rank (n=2).
v The following rules apply to single-rank and dual-rank DDR3 DIMM speed as it
relates to the number of DIMMs in a channel:
– When you install 1 DIMM per channel, the memory runs at 1333 MHz
– When you install 2 DIMMs per channel, the memory runs at 1066 MHz
– When you install 3 DIMMs per channel, the memory runs at 800 MHz
– All channels in a server run at the fastest common frequency
– Mixing registered and unbuffered DIMMs is not supported
v The maximum memory speed is determined by the combination of the
microprocessor, DIMM speed, and the number of DIMMs installed in each
channel.
Note: If you install two supported DDR3-1333 DIMMs in each channel on server
models with an Intel Xeon X5570 microprocessor, you must use the ASU
tool to set the server to operate at 1333 MHz in two-DIMM-per-channel
(2DPC) configuration (see the Problem Determination and Service Guide
for more information).
v The server supports a maximum of 16 single-rank or dual-rank DIMMs.
v The server supports three single-rank or dual-rank DIMMs per channel. The
following table shows an example of the maximum amount of memory that you
can install, using ranked DIMMs.
Table 9. Maximum memory installation using ranked DIMMs
Number of DIMMs DIMM type
16 Single-rank DIMMs
16 Dual-rank DIMMs
16 Dual-rank DIMMs
v The DIMM options that are available for the server are 1 GB, 2 GB, 4 GB, and 8
GB (when available). The server supports a minimum of 1 GB and a maximum of
128 GB of system memory.
Note: The amount of usable memory is reduced depending on the system
configuration. A certain amount of memory must be reserved for system
resources. To view the total amount of installed memory and the amount
of configured memory, run the Setup utility. For additional information, see
Chapter 3, "Configuring the server," on page 89.
v A minimum of one DIMM must be installed for each microprocessor. For
example, you must install a minimum of two DIMMs if the server has two
microprocessors installed. However, to improve system performance, install a
minimum of three DIMMs for each microprocessor.
v The maximum operating speed of the server is determined by the slowest DIMM
installed in the server.
v The server comes with a minimum of two 1 GB DIMMs, installed in slots 3 and 6.
When you install additional DIMMs, install them in the order shown in the
following table to optimize system performance. In non-mirroring mode, all three
channels on the memory interface for each microprocessor can be populated in
any order and have no matching requirements.
DIMM size Total memory
4 GB 64 GB
4 GB 64 GB
8 GB (when 128 GB
available)
Chapter 2. Installing optional devices
53