When you use memory mirroring, you must install two pairs of DIMMs at a time.The four DIMMs in each group must be identical. See Table 4 for the DIMMconnectors that are in each group.Table 4. Memory mirroring DIMM installation sequenceGroup DIMM connectors1 1, 4, 7, and 102 2, 5, 8, and 113 3, 6, 9, and 12Table 5. Memory mirroring DIMM functionsGroup Active DIMMs Mirroring DIMMs1 1, 4 7, 102 2, 5 8, 113 3, 6 9, 12Online-spare memoryThe server supports online-spare memory. This feature disables the failed memoryfrom the system configuration and activates an online-spare pair of DIMMs toreplace the failed active DIMM pair.Online-spare memory reduces the amount of available memory. Before you canenable this feature, you must install up to two additional pairs of DIMMs. Theonline-spare DIMM pairs must be the same speed, type, and the same size as, orlarger than, the largest active DIMM pairs.Enable online-spare memory through the Configuration/Setup Utility program. TheBIOS code assigns the online-spare DIMM pairs according to your DIMMconfiguration. Online-sparing is enabled on a memory branch basis; the BIOS codedoes not enable online-sparing on a branch that cannot support online-sparing. Seethe illustration on page 68 for the memory branch structure. DIMM ranks areonline-spared if the DIMMs are installed according to the rules in Table 6 on page71 or Table 7 on page 71.Note: POST gives a warning message when online-sparing cannot be enabled onboth branches. However, no warning message is given when online-sparing isenabled on one branch and disabled on the other.Online-spare configurations are supported for each branch. See Table 6 on page 71and Table 7 on page 71 for the online-spare DIMM connector assignments.Important: Table 6 on page 71 shows the basic DIMM online-spare scheme. If theBIOS code level is version 1.04 or later, you can install the DIMMs according to thealternative scheme, shown in Table 7 on page 71, instead.70 System x3650 Type 7979: User’s Guide
