Memory module installation - Lenovo System x3250 M5

The following notes 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 (see 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 that indicates that the memory configuration has changed. You can use the Setup utility to view the server configuration information, see Using the Setup utility for more information.
The server supports only industry-standard double-data-rate 3 (DDR3), 1333 or 1600 MHz, PC3L-12800 (single-rank or dual-rank), unbuffered or synchronous dynamic random-access memory (SDRAM) dual inline memory modules (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 connectors 1 and 3, the size and speed of the DIMMs that you install in DIMM connectors 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 connectors 2 and 4.
You can use compatible DIMMs from various manufacturers in the same pair.
The specifications of a DDR3 DIMM are on a label on the DIMM, in the following format.
gGBeRxf PC3v-wwwwwm-aa-bb-cc
where:
- gGB is the total capacity of the DIMM (for example, 1GB, 2GB, or 4GB)
- eR is the number of ranks
  - 1R = single-rank
  - 2R = dual-rank
  - 4R = quad-rank
- xf is the device organization or bit width (for example, x4, x8, or x16)
  - x4 = x4 organization (4 DQ lines per SDRAM)
  - x8 = x8 organization
  - x16 = x16 organization
- v is the SDRAM and support component supply voltage (VDD)
  - Blank = 1.5 V specified
  - L = 1.35 V specified, 1.5 V operable
    Note: Values for these voltages are ‘specified’ which means the device characteristics such as timing are supported at this voltage. Values are ‘operable’ which means that the devices can be operated safely at this voltage. However, device characteristics such as timing may not be guaranteed. All devices must be ‘tolerant’ of the highest DDR3 nominal voltage of 1.5 V, meaning that they may not operate at 1.5 V but may be powered at that voltage without damage to the devices.
  - wwwww is the DIMM bandwidth, in MBps
    - 6400 = 6.40 GBps (DDR3-800 SDRAMs, 8-byte primary data bus)
    - 8500 = 8.53 GBps (DDR3-1066 SDRAMs, 8-byte primary data bus)
    - 10600 = 10.66 GBps (DDR3-1333 SDRAMs, 8-byte primary data bus)
    - 12800 = 12.80 GBps (DDR3-1600 SDRAMs, 8-byte primary data bus)
  - m is the DIMM type
    - E = Unbuffered DIMM (UDIMM) with ECC (x72-bit module data bus)
    - R = Registered DIMM (RDIMM)
    - U = Unbuffered DIMM with no ECC (x64-bit primary data bus)
  - aa is the CAS latency, in clocks at maximum operating frequency
  - bb is the JEDEC SPD Revision Encoding and Additions level
  - cc is the reference design file for the design of the DIMM
Note:
1. To determine the type of a DIMM, see the label on the DIMM. The information on the label is in the format xGB nRxx PC3v-xxxxxx-xx-xx-xx. The numeral in the sixth numerical position indicates whether the DIMM is single-rank (n=1) or dual-rank (n=2).
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 the Setup utility. For additional information, see Configuring the server.

The following illustration shows the location of the DIMM connectors on the system board.

Figure 1. The location of the DIMM connectors on the system board

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