Installing an eXFlash DIMM

Use this information to install an eXFlash DIMM.

This component can be installed as an optional device or as a CRU. The installation procedure is the same for the optional device and the CRU.

The following illustration shows the system-board components, including the DIMM connectors.

The following notes describe information that you must consider when you install eXFlash DIMMs:

• Install only one eXFlash DIMM per channel with one or two DIMMs on the same channel.
  • The DIMM must always be installed in the terminating DIMM connector of the channel.
  • The eXFlash DIMM must be installed in the last channel after all DIMMs are installed. The eXFlash DIMM must be next to the DIMM with no empty DIMM connectors between the DIMM and the eXFlash DIMM.
• The number of DIMMs in a configuration must equal or exceed the number of eXFlash DIMMs.
• Do not install eXFlash DIMMs in DIMM connectors 31 through 42.
• The maximum number of eXFlash DIMMs and DIMMs is 48.
• Install only 200 GB eXFlash DIMMs or only 400 GB eXFlash DIMMs, mixing of capacities is not supported.
• You can install 2, 4, 8, or 12 eXFlash DIMMs in a compute node.
• Lockstep mode, mirrored-channel mode, and rank sparing are not supported when eXFlash DIMMs are installed.
• eXFlash DIMMs operate at the same DIMM frequency as the speed of the DIMMs installed in the compute node.
• In two-node and four-node complexes, you can install a maximum of 24 eXFlash DIMMs.
• You can install eXFlash DIMMs in only the two nodes in the lowest bay IDs in a four-node complex.
• eXFlash DIMMs operate only at 1.5 V.
• For supported operating conditions, see the eXFlash DIMM configuration and support requirements page.

Note: The amount of eXFlash DIMM storage that is displayed in the Setup utility might be different from the amount of eXFlash DIMM storage installed in the compute node.

If you plan to install eXFlash DIMMs, install the DIMMs in the Independent mode configuration as described in Table 2.

You install eXFlash DIMMs in groups. The following illustration shows the eXFlash DIMM groups and the DIMM connectors.

Consider the following requirements concerning eXFlash DIMM groups:

• Install the first eXFlash DIMM in group 1, the next eXFlash DIMM in group 2, and install subsequent eXFlash DIMMs in the next group in sequence.
• For configurations exceeding 32 DIMMs, if all DIMM connectors within a group are populated, install the eXFlash DIMMs starting with the lowest available group number.
• In an unbalanced DIMM configuration (that is, channels populated with unequal numbers of DIMMs), start the installation of the first eXFlash DIMM with the lowest group number containing the smallest number of DIMMs per channel. For example, if group 1 has 2 DIMMs and group 2 has 1 DIMM, start installation of eXFlash DIMMs in group 2. Continue the installation of eXFlash DIMMs in each group in a circular order across the system board.

To maintain maximum performance, consider the following information:

• Install DIMMs in a balanced configuration (that is, an even number of DIMMs across channels).
• Balance the number of DIMMs and eXFlash DIMMs between microprocessors.
• Install DIMMs in even-numbered quantities.
• For optimal performance, consider the following configurations.
  • 8 DIMMs configured with 2 or 4 eXFlash DIMMs
  • 16 DIMMs configured with 2, 4, 8, or 12 eXFlash DIMMs
  • 32 DIMMs configured with 2, 4, 8, or 12 eXFlash DIMMs
• More than 32 DIMMs might impact memory I/O performance because it creates an unbalanced memory configuration.

The following table shows sample DIMM and eXFlash DIMM configurations.

Table 1. Sample DIMM and eXFlash DIMM configurations.

Configuration	DIMMs	eXFlash DIMMs
18 DIMMs 4 eXFlash DIMMs	DIMM connectors: 28, 25, 10, 15, 4 ,21, 33, 40, 25, 48, 7, 18, 1, 24, 36 ,37 ,29, 44	eXFlash DIMMs installed in groups: 3, 4 ,5, 6 DIMM connectors: 11, 14, 5, 20
8 DIMMs 2 eXFlash DIMMs	DIMM connectors: 28, 25, 10, 15, 4, 21, 33, 40	eXFlash DIMMs installed in groups: 1, 2 DIMM connectors: 29, 44
32 DIMMs 12 eXFlash DIMMs	DIMM connectors: 28, 25, 10, 15, 4, 21, 33, 40, 25, 48, 7, 18, 1, 24 ,36, 37, 29, 44, 11,14, 5, 20, 32, 41, 26, 47, 8, 17, 2, 23, 35, 38	eXFlash DIMMs installed in groups: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 DIMM connectors: 30, 43, 12, 13, 6, 19, 27, 46, 9, 16, 3, 22

To install an eXFlash DIMM, complete the following steps:

1. Remove the cover (see Removing the compute node cover).
2. Read the documentation that comes with the eXFlash DIMM.
3. Remove the air baffle installed over the DIMM connector.
4. Locate the DIMM connectors (see System-board connectors). Determine in which DIMM connector you want to install the eXFlash DIMM.
5. Touch the static-protective package that contains the eXFlash DIMM to any unpainted metal surface on the Lenovo Flex System chassis or any unpainted metal surface on any other grounded rack component in the rack in which you are installing the eXFlash DIMM for at least 2 seconds; then, remove the eXFlash DIMM from the package.
   
   
6. Make sure that both retaining clips on the DIMM connector are in the open position.
7. Turn the eXFlash DIMM so that the eXFlash DIMM keys align correctly with the DIMM connector on the system board.
   Attention: To avoid breaking the retaining clips or damaging the DIMM connector, handle the clips gently.
8. Press the eXFlash DIMM into the DIMM connector. The retaining clips lock the eXFlash DIMM into the connector.
9. Make sure that the small tabs on the retaining clips engage the notches on the eXFlash DIMM. If there is a gap between the eXFlash DIMM and the retaining clips, the eXFlash DIMM has not been correctly installed. Press the eXFlash DIMM firmly into the connector, and then press the retaining clips toward the eXFlash DIMM until the tabs are fully seated. When the eXFlash DIMM is correctly installed, the retaining clips are parallel to the sides of the eXFlash DIMM.
10. Install the air baffle over the DIMM connector.
    Attention:

    • Install the air baffles with the arrow indicating air flow direction pointing to the rear of the compute node.
    • To maintain proper system cooling, do not operate the compute node without air baffles installed over the DIMM connectors.