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Memory module installation rules and order

Memory modules must be installed in a specific order based on the memory configuration that you implement and the number of processors and memory modules installed in the server.

Supported memory types

For information on the types of memory module supported by this server, see Memory section in Technical Specifications.

Your server has 24 memory slots with 24 channels. For a list of supported memory options, see:

Lenovo ServerProven website.

Information about optimizing memory performance and configuring memory is available at the Lenovo Press website:

Memory - Lenovo Press

In addition, you can take advantage of a memory configurator, which is available at the following site:

Lenovo Enterprise Solutions Configurator (Memory Configurations)

Specific information about the required installation order of memory modules in your server based on the system configuration and memory mode that you are implementing is shown below.

Your server has 24 channels, 24 memory slots, and supports:
  • Minimum memory: 16 GB

  • Maximum memory:

    • RDIMM: 2.25 TB: 24 x 96 GB RDIMMs

    • 3DS RDIMM: 6 TB using 24 x 256 GB RDIMMs

  • Type (depending on the model):

    • TruDDR5 4800, single-rank, 16 GB/32 GB RDIMM

    • TruDDR5 4800, dual-rank, 32 GB/64 GB/96 GB RDIMM

    • TruDDR5 4800, quad-rank, 128 GB 3DS RDIMM

    • TruDDR5 4800, octal-rank, 256 GB 3DS RDIMM

The following illustration helps you to locate the memory module slots on the system board (system board assembly).
It is recommended to install memory modules with the same rank in each channel.
Figure 1. Memory modules and processors layout
Memory module slots on the system board (system board assembly)

The memory-channel configuration table below shows the relationship between the processors, memory controllers, memory channels, and memory module slot numbers.

Table 1. Memory slot and channel identification
ProcessorProcessor 2 Processor 1
UMC No.2150439106117821504391061178
DIMM No.242322212019181716151413121110987654321

General DIMM mixing rules

DIMMsCoexist in a system
3DS RDIMMs and other DIMM typesX
128 GB 3DS RDIMMs and 256 GB 3DS RDIMMsX
x4 DIMMs and x8 DIMMsX
16 Gbit (16 GB/32 GB/64 GB) DIMMs and 24 Gbit (96 GB) DIMMsX
ThinkSystem 128GB TruDDR5 4800MHz (4Rx4) 3DS RDIMM-A v1 and ThinkSystem 128GB TruDDR5 4800MHz (4Rx4) 3DS RDIMM-A v2X
DIMMs manufactured by different vendors
DIMMs of different rank2
DIMMs of different capacity3
DIMMs of different frequency/speed4
  1. Only support ECC DIMMs.

  2. Install the DIMM with the higher rank first.

  3. Install the DIMM with the higher capacity first following the population sequence.

  4. DIMMs should run at the supported frequency/speed on the system. (Maximum frequency: 4800 MT/s).

Memory module installation order

In the following tables:
  • S1–S24 indicate DIMM slots 1–24.

  • 1–24 indicate the installation order.

For example, when 12 DIMMs are installed for two processors, the installation order is slot 7, 19, 6, 18, 9, 21, 4, 16, 8, 20, 5, 17.

Server model with one processor

The following table shows the DIMM population sequence when one processor is installed.

Table 2. DIMM population sequence for one processor
Total DIMMsProcessor 1
2 DIMMs     12     
4 DIMMs3124
6 DIMMs   351264   
8 DIMMs73512648
10 DIMMs 79351264108 
12 DIMMs117935126410812

Server model with two processors

The following table shows the DIMM population sequence when two processors are installed.

Table 3. DIMM population sequence for two processors
Total DIMMsProcessor 1
2 DIMMs1
4 DIMMs     13     
8 DIMMs5137
12 DIMMs   5913117   
16 DIMMs13591311715
20 DIMMs 131759131171915 
24 DIMMs2113175913117191523
Total DIMMsProcessor 2
2 DIMMs2
4 DIMMs     24     
8 DIMMs6248
12 DIMMs   61024128   
16 DIMMs146102412816
20 DIMMs 1418610241282016 
24 DIMMs22141861024128201624