In rank-sparing mode, one rank is held in reserve as a spare of the other ranks in the same channel.
If an error threshold is surpassed in an active rank, the contents of that rank are copied to the spare rank in the same channel. The failed rank is taken offline, and the spare rank becomes active. Rank sparing in a channel is independent of rank sparing in other channels.
If a channel contains only one DIMM and the DIMM is single-rank or dual-rank, do not attempt to use rank sparing. At least one DIMM pair must be installed for each microprocessor. If you are using all quad-rank DIMMs, use the installation sequence for independent-channel mode (see
Table 1). If you are using a combination of single-rank, dual-rank, and quad-rank DIMMs, install DIMMs in the order shown in the following table.
Table 1. Rank-sparing mode DIMM installation sequence. The rank-sparing mode DIMM installation sequence table is a three-column table where the rows indicate the DIMM installation sequence for rank-sparing mode. Column 1 lists the DIMM installation order. Column 2 indicates the DIMM connectors to populate for systems with one microprocessor. Column 3 indicates the DIMM connectors to populate for systems with two microprocessors.
| Installation order | DIMM connectors |
|---|
| With one microprocessor | With two microprocessors |
|---|
| 1 | 5 and 6 | 5 and 6, 7 and 8 |
| 2 | 3 and 4 | 3 and 4 |
| 3 | 1 and 2 | 9 and 10 |
| 4 | - | 1 and 2 |
| 5 | - | 11 and 12 |