Dell PowerEdge M620 Hardware Owner's Manual - Page 208

Non-Optimal Memory Configurations System performance can be affected if your memory configuration does not conform to the preceding installation guidelines. Your system may issue an error message during start-up stating that your memory configuration is nonoptimal. Memory Sparing Support - PowerEdge M605 Memory sparing is supported in single- or dual-processor systems that have one of the fully populated memory configurations shown in Table 3-13. The memory sparing feature must be enabled in the Memory Information screen of the System Setup program. See "Memory Settings Screen" on page 140. To use memory sparing, you must disable node interleaving. Memory sparing allocates only the first rank of memory of a DIMM. For a single-rank DIMM, the entire capacity of the DIMM must be allocated for sparing along with the adjacent single-rank DIMM to spare a memory channel. For dual-rank DIMMs, two DIMMs are also required for sparing, but as only the first rank of each DIMM is allocated, only half of a dual-rank DIMM's capacity is allocated for sparing. The second ranks on both DIMMs are available memory. Table 3-13 shows how memory sparing splits the available and spared memory in each memory module configuration. 208 Installing Blade Components