Lenovo TD100X manual Both branches operate in dual-channel mode

vThe server supports memory mirroring (mirroring mode) and online-spare memory.

–Memory mirroring replicates and stores data on DIMMs within two branches simultaneously. You must enable memory mirroring through the Configuration/Setup Utility program. To enable memory mirroring in the Configuration/Setup Utility program, select Devices and I/O Ports → Advanced Chipset Control → Memory Branch Mode. Use the arrow keys to change the Memory Branch Mode setting to Mirror; then, save your changes. For more information on the Configuration/Setup Utility program, see the User Guide. When you use memory mirroring, consider the following information:

-For ThinkServer TD100 models, the maximum available memory is reduced to 16 GB, instead of the 32 GB available in non-mirroring mode.

-For ThinkServer TD100x models, the maximum available memory is reduced to 24 GB, instead of the 48 GB available in non-mirroring mode.

-The minimum memory configuration is four identical DIMMs. You must install identical pairs of fully buffered, dual-inline memory modules (DIMMs) in all four DIMM connectors (same size, type, speed, and technology). These DIMMs must span across both branches and all four channels. For example, when you install the first four DIMMs, you must install two DIMMs in branch 0 (one in channel 0 and one in channel 1) and two DIMMs in branch 1 (one in channel 2 and one in channel 3). See Table 15 for the DIMM installation sequence.

-When you upgrade the server to eight or 12 DIMMs, the DIMMs that are next to each other (for example, DIMM connector 1 and DIMM connector 4) within the channels of a branch must be identical in size, type, speed, and technology. However, the DIMMs in the connectors above or below each other within the channels of a branch do not have to be identical to each other (for example, the DIMMs in DIMM connector 1 and DIMM connector 2).

-Both branches operate in dual-channel mode.

The following table shows the DIMM configuration upgrade sequence for operating in mirroring mode.

Table 15. DIMM upgrade configuration sequence in mirroring mode

Number of DIMMs	DIMM connectors
4	1, 4, 7, 10
8	1, 4, 7, 10, 2, 5, 8, 11
12 (ThinkServer TD100x Machine Types	1, 4, 7, 10, 2, 5, 8, 11, 3, 6, 9, 12
4203, 4204, 4205, and 4206)

Note: For ThinkServer TD100 models (Machine Types 6398, 6399, 6419, 6429, 4203, and 4206), DIMM connectors 3, 6, 9, and 12 are not functional. Do not install DIMMs in these connectors.

–Online-spare memory disables a failed rank pair of DIMMs from the system configuration and activates an online-spare rank pair of DIMMs to replace the failed rank pair of DIMMs. For an online-spare pair of DIMMs to be activated, you must enable this feature and have installed an additional rank pair of DIMMs of the same speed, type, size (or larger), and technology as the failed pair of DIMMs. You must enable the feature through the Configuration/Setup Utility program. To enable online-spare memory in the Configuration/Setup Utility program, select Devices and I/O Ports → Advanced Chipset Control → Memory Branch Mode. Use the arrow keys to change the setting for Branch 0 Rank Sparing or Branch 1 Rank Sparing to Enabled; then, save your

Chapter 4. Removing and replacing server components 99