General memory module installation guidelinesNOTE: Memory configurations that fail to observe these guidelines can prevent your system from booting, stop respondingduring memory configuration, or operate with reduced memory.The system supports Flexible Memory Configuration, enabling the system to be configured and run in any valid chipset architecturalconfiguration. The following are the recommended guidelines for installing memory modules:• RDIMMs and LRDIMMs must not be mixed.• x4 and x8 DRAM based memory modules can be mixed. For more information, see the Mode-specific guidelines section.• Up to two RDIMMs can be populated per channel regardless of rank count.• Up to two LRDIMMs can be populated per channel regardless of rank count.• If memory modules with different speeds are installed, they will operate at the speed of the slowest installed memory module(s) orslower depending on the system DIMM configuration.• Populate memory module sockets only if a processor is installed. For single-processor systems, sockets A1 to A12 are available. For dual-processor systems, sockets A1 to A12 and sockets B1 to B12 are available.• Populate all the sockets with white release tabs first, followed by the black release tabs.• When mixing memory modules with different capacities, populate the sockets with memory modules with highest capacity first. Forexample, if you want to mix 8 GB and 16 GB memory modules, populate 16 GB memory modules in the sockets with white release tabsand 8 GB memory modules in the sockets with black release tabs.• In a dual-processor configuration, the memory configuration for each processor should be identical. For example, if you populate socketA1 for processor 1, then populate socket B1 for processor 2, and so on.• Memory modules of different capacities can be mixed provided other memory population rules are followed (for example, 8 GB and 16GB memory modules can be mixed).• Mixing of more than two memory module capacities in a system is not supported.• Populate six memory modules per processor (one DIMM per channel) at a time to maximize performance.NVDIMM-N memory module installation guidelinesThe following are the recommended guidelines for installing NVDIMM-N memory modules:• Each system supports memory configurations with 1, 2, 4, 6, or 12 NVDIMM-Ns.• Supported configurations have dual processors and a minimum of 12x RDIMMs.• LRDIMMS and NVDIMM-Ns must not be mixed.• Maximum of 12 NVDIMM-Ns can be installed in a system.The following table lists the NVDIMM-N configurations that are currently supported on your system.Table 39. Supported NVDIMM-N configurationsConfiguration Description Memory population rulesConfiguration 1 12x 16 GB RDIMMs, 1x NVDIMM-N RDIMMs – C1{1,2,3,4,5,6}, C2{1,2,3,4,5,6}NVDIMM-N – C1{7}Configuration 2 12x 32 GB RDIMMs, 1x NVDIMM-N RDIMMs – Same for all 12x RDIMMconfigurations. See Configuration 1NVDIMM-N – C1{7},C2{7}Dell EMC PowerEdge R640 Installation and Service ManualInstalling and removing system components81
