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Independent memory mode

In independent memory mode, memory channels can be populated with DIMMs in any order. All channels for each processor can be populated 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 the independent memory mode varies based on the number of processors and memory modules installed in the server.

Memory module installation order in independent mode

Follow the rules below when installing memory modules in independent mode:
  • All memory modules must be DDR5 memory modules.

  • At least one DDR5 DIMM is required per installed processor.

  • All DDR5 DIMM must operate at the same speed in the same system.

  • Memory population must be identical between processors.

  • Memory modules from different vendors are supported.

  • In each memory channel, populate the slot farthest from the processor (slot 0) first.

  • x8 DIMMs and x4 DIMMs cannot be mixed in a system.

  • All memory modules to be installed must be of the same type.

    • 9x4 RDIMM cannot be mixed with non-9x4 RDIMMs in a system.

    • 3DS RDIMM cannot be mixed with non-3DS RDIMMs in a system.

  • All memory modules in a system must have the same number of ranks, except for the conditions below:

    • Single-ranked RDIMMS can be mixed with dual-rank RDIMMs when there are 16 DIMMs populated for each processor (i.e., either 16 or 32 DIMMs in total).

    Note
    System hang on POST may occur on a server operation in this configuration. In this case, contact Lenovo service to replace the failed DIMM for proper operation.

     

  • See Independent memory mode with mixing ranks for more information on the installation sequence when installing memory modules with different ranks.

With one processor

Table 1. Independent memory mode with one processor
  • Processor 1
  • Total DIMMs
12345678910111213141516
  • 1
  • DIMM
         10      
  • 2
  • DIMMs
  3      10      
  • 4
  • DIMMs1
  3   7  10   14  
  • 6
  • DIMMs
  3 5 7  10   14 16
  • 8
  • DIMMs1,2
1 3 5 7  10 12 14 16
  • 12
  • DIMMs
1 345 78910 121314 16
  • 16
  • DIMMs1,2,3
12345678910111213141516
Note
  1. Sub NUMA Clustering (SNC2) feature can only be enabled when DIMMs are populated in this specified sequence. The SNC2 feature can be enabled via UEFI.
  2. DIMM configurations that support Software Guard Extensions (SGX), see Enable Software Guard Extensions (SGX) to enable this feature.

  3. In ThinkSystem ST650 V3, rank mixing is supported between single-rank and dual-rank RDIMMs when there are 16 DIMMs populated for each processor. See Independent memory mode with mixing ranks for more information on the installation sequence when installing memory modules with different ranks.

With two processors

Table 2. Independent mode with two processors
  • Processor 1
  • Total DIMMs
12345678910111213141516
  • 2
  • DIMMs
          10      
  • 4
  • DIMMs1
  3      10      
  • 8
  • DIMMs1,2
  3   7  10   14  
  • 12
  • DIMMs
  3 5 7  10   14 16
  • 16
  • DIMMs1,2
1 3 5 7  10 12 14 16
  • 24
  • DIMMs
1 345 78 910 121314 16
  • 32
  • DIMMs1,2
12345678910111213141516
  • Processor 2
  • Total DIMMs
32313029282726252423222120191817
  • 2
  • DIMMs
         23      
  • 4
  • DIMMs1
  30      23      
  • 8
  • DIMMs1,2
  30   26  23   19  
  • 12
  • DIMMs
  30 28 26  23   19 17
  • 16
  • DIMMs
32 30 28 26  23 21 19 17
  • 24
  • DIMMs
32 302928 26252423 212019 17
  • 32
  • DIMMs1,2,3
32313029282726252423222120191817

Note
  1. Sub NUMA Clustering (SNC2) feature can only be enabled when DIMMs are populated in this specified sequence. The SNC2 feature can be enabled via UEFI.
  2. DIMM configurations that support Software Guard Extensions (SGX), see Enable Software Guard Extensions (SGX) to enable this feature.

  3. In ThinkSystem ST650 V3, rank mixing is supported between single-rank and dual-rank RDIMMs when there are 16 DIMMs populated for each processor. See Independent memory mode with mixing ranks for more information on the installation sequence when installing memory modules with different ranks.