IBM System x3550 M4 Installation And Service Manual page 69

v The maximum memory speed is determined by the combination of the
microprocessor, DIMM speed, DIMM type, Operating Modes in UEFI settings,
and the number of DIMMs installed in each channel.
v In two-DIMM-per-channel configuration, the server automatically operates with
a maximum memory speed of up to 1600 MHz when the following condition is
met:
– Two 1.35 V single-rank, dual-ranl, or quad-rank UDIMMs, RDIMMs or
LRDIMMs are installed in the same channel. In the Setup utility, Memory
speed is set to Max performance and LV-DIMM power is set to Enhance
performance mode. The 1.35 V UDIMMs, RDIMMs or LRDIMMs will
function at 1.5 V.
v The server supports a maximum of 16 dual-rank UDIMMs. The server supports
up to two UDIMMs per channel.
v The server supports a maximum of 24 single-rank, dual-rank, or 16 quad-rank
RDIMMs. The server does not support three quad-rank RDIMMs in the same
channel.
v The following table shows an example of the maximum amount of memory that
you can install using ranked DIMMs:
Table 5. Maximum memory installation using ranked DIMMs
Number of
DIMMs DIMM type
16 Dual-rank UDIMM
24 Single-rank RDIMM
24 Single-rank RDIMM
24 Dual-rank RDIMM
24 Dual-rank RDIMM
24 Dual-rank RDIMM
16 Quad-rank RDIMM
24 Quad-rank LRDIMM
v The UDIMM option that is available for the server is 4 GB. The server supports
a minimum of 4 GB and a maximum of 64 GB of system memory using
UDIMMs.
v The RDIMM options that are available for the server are 2 GB, 4 GB, 8 GB, and
16 GB. The server supports a minimum of 2 GB and a maximum of 384 GB of
system memory using RDIMMs.
v The LRDIMM option that is available for the server is 32 GB. The server
supports a minimum of 32 GB and a maximum of 768 GB of system memory
using LRDIMMs.
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
"Configuring the server" on page 102.
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 four DIMMs for each microprocessor.
DIMM size Total memory
4 GB 64 GB
2 GB 48 GB
4 GB 96 GB
4 GB 96 GB
8 GB 192 GB
16 GB 384 GB
8 GB 128 GB
32 GB 768 GB
Chapter 2. Installing optional devices
51