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DIMM installation guidelines

The following tips describe the types of DIMMs that the server supports and other information that you must consider when you install DIMMs.

  • Confirm that the server supports the DIMM that you are installing. Go to: the Lenovo ServerProven website
  • When you install or remove DIMMs, the server configuration information changes. When you restart the server, the system displays a message indicating that the memory configuration has been changed. You can use the Setup Utility program to view the server configuration information. See Using the Setup Utility program.
  • The server supports only industry-standard DDR4, 2133 MHz, PC4-17000 (single-rank or dual-rank), unbuffered DIMMs with error correcting code (ECC).
  • The server supports a maximum of four single-rank or dual-rank unbuffered DIMMs.
  • The maximum operating speed of the server is determined by the slowest DIMM in the server.
  • If you install a pair of DIMMs in DIMM slots 3 and 1, the size and speed of the DIMMs that you install in DIMM slots 1 and 3 must match each other. However, they do not have to be the same size and speed as the DIMMs that are installed in DIMM slots 4 and 2.
  • You can use compatible DIMMs from various manufacturers in the same pair.
  • To determine the type of a DIMM, see the label on the DIMM. The information on the label is in the format x GB nRxx PC4-xxxxxx-xx-xx-xx. The nRxx indicates whether the DIMM is single-rank (n=1) or dual-rank (n=2).
  • 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 Setup Utility. For additional information, see Configuring the server.
  • The specifications of a DDR4 DIMM are on a label on the DIMM, in the following format:

    gggGBpheRxff PC4-wwwwaa-mccd-bb

    where:
    • gggGB is the total capacity of the DIMM (for example, 1 GB, 2 GB, or 4 GB)
    • pheR is the number of package ranks and number of logical ranks per package rank p has the following variables:
      • 1 = 1 package rank of SDRAMs installed
      • 2 = 2 package ranks of SDRAMs installed
      • 3 = 3 package ranks of SDRAMs installed
      • 4 = 4 package ranks of SDRAMs installed

    • he: blank for monolithic DRAMs and others for modules using stacked DRAM

      . h is the DRAM package type. It has the following variables:
      • D = multi-load DRAM stacking (DDP)
      • Q = multi-load DRAM stacking (QDP)
      • D = single load DRAM stacking (3DS)
      e: blank for SDP, DDP and QDP and others for modules using 3DS stacks, logical ranks per package rank It has the following variables:
      • 2 = 2 logical ranks in each package rank
      • 4 = 4 logical ranks in each package rank
      • 8 = 8 logical ranks in each package rank
    • xff is the device organization or bit width of SDRAMs (for example, x4, x8, or x16)
      • x4 = x4 organization (four DQ lines per SDRAM)
      • x8 = x8 organization
      • x16 = x16 organization
    • wwww is the DIMM speed, in MBps (for example, 2133, 2400, 2666, 2933, or 3200) aa is the SDRAM speed grade
    • m is the DIMM type
      • E = Unbuffered DIMM (UDIMM) (x64-bit primary data bus) with ECC (x8-bit module data bus)
      • L = Load Reduced DIMM (LRDIMM) (x64-bit primary data bus) with ECC (x8-bit module data bus)
      • R = Registered DIMM (RDIMM) (x64-bit primary data bus) with ECC (x8-bit module data bus)
      • U = Unbuffered DIMM with no ECC (x64-bit primary data bus)

      cc is the reference design file for the design of the DIMM

      d is the revision number of the used reference design

    • bb is the JEDEC SPD Revision Encoding and Additions level

To locate the DIMM slots on the system board, see System-board connectors.

The following sections provide additional information specific to unbuffered DIMMs that you must consider.