Lenovo ThinkSystem SR650 V2 Maintenance Manual page 264

– "DRAM DIMM installation order" on page 254 (RDIMMs or 3DS RDIMMs)
– "PMEM and DRAM DIMM installation order" on page 259
• A label on each DIMM identifies the DIMM type. This information is in the format xxxxx nRxxx PC4-
xxxxx-xx-xx-xxx. Where n indicates if the DIMM is single-rank (n=1) or dual-rank (n=2).
• At least one DIMM is required for each processor. Install at least eight DIMMs per processor for good
performance.
• When you replace a DIMM, the server provides automatic DIMM enablement capability without requiring
you to use the Setup utility to enable the new DIMM manually.
Attention:
• Mixing x4 and x8 DIMMs in the same channel is allowed.
• Always populate DIMMs with the maximum number of ranks in the farthest DIMM slot, followed by the
nearest DIMM slot.
• Do not mix RDIMMs and 3DS RDIMMs in the same server.
DRAM DIMM installation order
For RDIMMs or 3DS RDIMMs, the following memory modes are available:
• "Independent mode" on page 254
• "Mirroring mode" on page 258
Independent mode
In independent memory mode, memory channels can be populated with DIMMs in any order and you can
populate all channels for each processor in any order with no matching requirements. Independent memory
mode provides the highest level of memory performance, but lacks failover protection. The DIMM installation
order for independent memory mode varies based on the number of processors and memory modules
installed in the server.
Follow the rules below when installing memory modules in independent mode:
• All memory modules to be installed must be of the same type. x4 and x8 DIMMs can be mixed in the same
channel.
• Memory modules from different vendors are supported.
• There must be at least one DDR4 DIMM per socket.
• In each memory channel, populate slot 0 first.
• If a memory channel has two DIMMs, populate the DIMM with a higher number of ranks in slot 0; if the two
DIMMs have the same number of ranks, populate the DIMM with a higher capacity in slot 0.
• A maximum of 8 logical ranks (ranks seen by the host) per channel is allowed.
• A maximum of two different DIMM capacities are supported per system.
– For channels A, C, E, and G, populated DIMMs must have the same total capacity for each channel.
– For channels B, D, F, and H, populated DIMMs must have the same total capacity for each channel,
which can be different from that of the other set (channels A, C, E, and G).
• If there are more than two DIMMs, populate them in a right-and-left symmetrical manner across a CPU
socket.
ThinkSystem SR650 V2Maintenance Manual
254