Table 9. Maximum memory installation using ranked DIMMs (continued)Number of DIMMs DIMM type DIMM size Total memory18 Dual-rank RDIMMs 2 GB 36 GB18 Dual-rank RDIMMs 4 GB 72 GB18 Dual-rank RDIMMs 8 GB 144 GB12 Quad-rank RDIMMs 16 GB 192 GB18 Dual-rank RDIMMs 16 GB 288 GBv The RDIMM options that are available for the server are 2 GB, 4 GB, 8 GB, and16 GB. The server supports a minimum of 2 GB and a maximum of 288 GB ofsystem memory using RDIMMs.For 32-bit operating systems only: Some memory is reserved for various systemresources and is unavailable to the operating system. The amount of memorythat is reserved for system resources depends on the operating system, theconfiguration of the server, and the configured PCI devices.v The UDIMM options that are available for the server are 2 GB and 4 GB. Theserver supports a minimum of 2 GB and a maximum of 48 GB of systemmemory using UDIMMs.Note: The amount of usable memory is reduced depending on the systemconfiguration. A certain amount of memory must be reserved for systemresources. To view the total amount of installed memory and the amount ofconfigured memory, run the Setup utility. For additional information, seeChapter 3, “Configuring the server,” on page 157.v A minimum of one DIMM must be installed for each microprocessor. Forexample, you must install a minimum of two DIMMs if the server has twomicroprocessors installed. However, to improve system performance, install aminimum of three DIMMs for each microprocessor.v DIMMs in the same system must be the same type (UDIMM or RDIMM) toensure that the server will operate correctly.v When you install one quad-rank RDIMM in a channel, install it in the DIMMconnector furthest away from the microprocessor.v Do not install one quad-rank RDIMM in one channel and three RDIMMs inanother channel.DIMM installation sequenceThe server comes with a minimum of one 2 GB DIMM installed in slot 3. Whenyou install additional DIMMs, install them in the order shown in the followingtable to optimize system performance. In non-mirroring mode, all three channelson the memory interface for each microprocessor can be populated in any orderand have no matching requirements.When you install additional DIMMs, installthem in the order shown in Table 10, to maintain performance.Important: If you have configured the server to use memory mirroring, do not usethe order in Table 10; go to “Memory mirroring” on page 119 and use theinstallation order shown there.Table 10. DIMM installation sequence for non-mirroring (normal) modeInstalled microprocessors DIMM connector population sequenceMicroprocessor socket 1 Install the DIMMs in the following sequence: 3, 6, 9, 2, 5, 8,1, 4, 7118 System x3650 M3 Types 4255, 7945, and 7949: Installation and User’s Guide
