Lenovo ThinkSystem ST550 Product Manual page 21

Memory options
The ST550 server supports Lenovo TruDDR4 memory. TruDDR4 memory uses the highest-quality
components sourced from Tier 1 DRAM suppliers and only memory that meets strict requirements is
selected. It is compatibility-tested and tuned to maximize performance and reliability.
TruDDR4 memory has a unique signature programmed into the DIMM, which enables ThinkSystem servers
to verify whether the memory installed is qualified and supported. From a service and support standpoint,
TruDDR4 memory automatically assumes the system's warranty, and service and support provided
worldwide.
The ST550 supports up to 6 DIMMs per processor, for a total of 12 DIMMs when two processors are
installed. Each processor has six memory channels, and supports one DIMM per channel.
All DIMMs operate at a speed of 2666 MHz. However, if the processor selected has a lower memory bus
speed (eg 2400 MHz or 2133 MHz - see the
lower speed.
The following table lists the memory options that are available for the ST550 server.
Table 12. Memory options
Part Feature
number code
RDIMMs
7X77A01301 AUU1
7X77A01302 AUNB
7X77A01304 AUND
LRDIMMs
7X77A01305 AUNE
The following rules apply when selecting the memory configuration:
The server supports RDIMMs and LRDIMMs.i
Mixing RDIMMs and LRDIMMs is not supported.
Mixing x4 and x8 DIMMs is supported.
For best performance, populate memory DIMMs in quantities of 6 per processor, so that all memory
channels are used.
The following memory protection technologies are supported:
ECC
Chipkill (for x4-based memory DIMMs; look for "x4" in the DIMM description)
Memory channel mirroring
Memory rank sparing
If memory channel mirroring is used, then DIMMs must be installed in pairs (minimum of one pair per
processor), and both DIMMs in a pair must be identical in type and size. 50% of the installed capacity is
available to the operating system.
If memory rank sparing is used, then a minimum of one quad-rank DIMM or two single-rank or dual-rank
DIMMs must be installed per populated channel (the DIMMs do not need to be identical). In rank sparing
mode, one rank of a DIMM in each populated channel is reserved as spare memory. The largest rank in
the channel will be automatically selected as the spare rank. The amount of memory available to the
operating system depends on the number, capacity and rank counts of the DIMMs installed.
Lenovo ThinkSystem ST550 Server
Processor options
Description
ThinkSystem 8GB TruDDR4 2666 MHz (1Rx8 1.2V) RDIMM
ThinkSystem 16GB TruDDR4 2666 MHz (1Rx4 1.2V) RDIMM
ThinkSystem 32GB TruDDR4 2666 MHz (2Rx4 1.2V) RDIMM
ThinkSystem 64GB TruDDR4 2666 MHz (4Rx4 1.2V) LRDIMM
table), then all DIMMs will operate at that
Maximum
supported
12 (6 per processor)
12 (6 per processor)
12 (6 per processor)
12 (6 per processor)
21