the order shown in the following table to optimize system performance. Innon-mirroring mode, all three channels on the memory interface for eachmicroprocessor can be populated in any order and have no matching requirements.Table 8. Non-mirroring (normal) mode DIMM installation sequenceInstalled microprocessors DIMM connector population sequenceMicroprocessor socket 1 3, 6, 9, 2, 5, 8, 1, 4, 7Microprocessor socket 2 12, 15, 18, 11, 14, 17, 10, 13, 16Memory mirroringMemory-mirroring mode replicates and stores data on two pairs of DIMMs withintwo channels simultaneously. If a failure occurs, the memory controller switchesfrom the primary pair of memory DIMMs to the backup pair of DIMMs. To enablememory mirroring through the Setup utility, select System Settings → Memory. Formore information, see “Using the Setup utility” on page 108. When you use thememory mirroring feature, consider the following information:v When 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 sameslot in channel 1. The two DIMMs in each pair must be identical in size, type,and rank (single or dual) , and organization, but not in speed. The channels runat the speed of the slowest DIMM in any of the channels.v Channel 2, DIMM connectors 7, 8, 9, 16, 17, and 18 are not used inmemory-mirroring mode.v The maximum available memory is reduced to half of the installed memory whenmemory mirroring is enabled. For example, if you install 64 GB of memory usingRDIMMs, only 32 GB of addressable memory is available when you use memorymirroring.The following diagram shows the memory channel interface layout with the DIMMinstallation sequence for mirroring mode. The numbers within the boxes indicate theDIMM population sequence in pairs within the channels, and the numbers next tothe boxes indicate the DIMM connectors within the channels. For example, thefollowing illustration shows the first pair of DIMMs (indicated by ones (1) inside theboxes) should be installed in DIMM connectors 1 on channel 0 and DIMMconnector 2 on channel 1. DIMM connectors 3, 6, 9, 12, 15, and 18 on channel 2are not used in memory-mirroring mode.The following table lists the DIMM connectors on each memory channel.CH0CH1CH2CPU1112233362 15 48 7CH2CH0CH14461210 1115161413QPI5569 1817CPU2Figure 1. Memory channel interface layoutChapter 2. Installing optional devices 59
