Lenovo 3797 manual Dimm installation sequence, Memory mirroring

DIMM installation sequence

The server requires at least one DIMM per microprocessor. The server comes with a minimum of two 1 GB DIMMs, installed in connectors 3 and 6. (Connectors 3 and 6 are the farthest connectors for channels 0 and 1 of microprocessor 1.) When you install additional DIMMs, install them in the order shown in Table 8, to maintain performance.

Important: If you have configured the server to use memory mirroring, do not use the order in Table 8; go to “Memory mirroring” and use the installation order shown there.

Table 8. DIMM installation sequence for non-mirroring (normal) mode

Installed microprocessors	DIMM connector population sequence
Microprocessor socket 1	Install the DIMMs in the following sequence: 3, 6, 8, 2, 5, 7,
	1, 4
Microprocessor socket 2	Install the DIMMs in the following sequence: 11, 14, 16, 10,
	13, 15, 9, 12

Memory mirroring

Memory-mirroring mode replicates and stores data on two pairs of DIMMs within two channels simultaneously. If a failure occurs, the memory controller switches from the primary pair of memory DIMMs to the backup pair of DIMMs. You must enable memory mirroring through the Setup utility. For details about enabling memory mirroring, see “Using the Setup Utility program” on page 104. When you use the memory mirroring feature, consider the following information:

vWhen you use memory mirroring, you must install a pair of DIMMs at a time. One DIMM must be in channel 0, and the mirroring DIMM must be in the same connector in channel 1. The two DIMMs in each pair must be identical in size, type, rank (single, dual, or quad), and organization. They do not have to be identical in speed. The channels run at the speed of the slowest DIMM in any of the channels. See Table 10 on page 68 for the DIMM connectors that are in each pair.

vChannel 2, DIMM connectors 8 ,7, 15, and 16 are not used in memory-mirroring mode.

vThe maximum available memory is reduced to half of the installed memory when memory mirroring is enabled. For example, if you install 64 GB of memory, only 32 GB of addressable memory is available when you use memory mirroring.

The following illustration shows the memory channel interface layout with the DIMM installation sequence for mirroring mode. The numbers within the boxes indicate the DIMM population sequence in pairs within the channels, and the numbers next to the boxes indicate the DIMM connectors within the channels. For example, the following illustration shows that the first pair of DIMMs (indicated by ones (1) inside the boxes) should be installed in DIMM connector 3 on channel 0 and DIMM connector 6 on channel 1. DIMM connectors 7, 8, 15, and 16 on channel 2 are not used in memory-mirroring mode.

66ThinkServer RD220 Types 3729, 3779, 3797, and 3798: Installation and User Guide