Dell PowerEdge R920 Dell PowerEdge R920 System Owners Manual - Page 42

DIMM Type LRDIMM DIMMs DIMM Size Populated/ Channel (DPC) 3 16 GB 1 32 GB / 64 GB 2 32 GB / 64 GB 3 32 GB / 64 GB Operating Frequency (in MT/s) DDR3 (1.5 V) 1066 1600 1600 1333 and 1066 DDR3 (1.35 V) Not Applicable 1333 1333 Not Applicable Maximum DIMM Rank/ Channel Dual rank Quad rank physical Quad rank physical Quad rank physical General Memory Module Installation Guidelines Your system supports Flexible Memory Configuration, enabling the system to be configured and run in any valid chipset architectural configuration. The following are the recommended guidelines for best performance: • RDIMMs and LRDIMMs must not be mixed. • x4 and x8 DRAM based DIMMs can be mixed. For more information, see Mode-Specific Guidelines. • One quad-rank RDIMM and up to three dual- or single-rank RDIMMs can be populated per channel. When a quad- rank RDIMM is populated in the first slot with white release levers, the third DIMM slot in the channel with green release lever cannot be populated. • Up to three LRDIMMs can be populated regardless of rank count. • Populate DIMM sockets only if a processor is installed. For dual-processor systems, sockets A1 to A12, B1 to B12 and sockets C1 to C12, D1 to D12 are available. Each processor requires a minimum of 2 DIMMs, which must be identical. • Populate all sockets with white release lever first, then black, and then green. • Do not populate the third DIMM socket in a channel with green release lever, if a quad-rank RDIMM is populated in the first socket with white release lever. • Populate the sockets by highest rank count in the following order - first in sockets with white release levers, then black, and then green. For example, if you want to mix quad-rank and dual-rank DIMMs, populate quad-rank DIMMs in the sockets with white release tabs and dual-rank DIMMs in the sockets with black release tabs. • The memory configuration for each processor should be identical. For example, if you populate socket A1 and B1 for processor 1, then populate socket C1 and D1 for processor 2, and so on. • Memory modules of different sizes can be mixed provided that other memory population rules are followed (for example, 4 GB and 8 GB memory modules can be mixed). • Populate four DIMMs per processor (one DIMM per channel) at a time to maximize performance. • If memory modules with different speeds are installed, they will operate at the speed of the slowest installed memory module(s) or slower depending on system DIMM configuration. Mode-Specific Guidelines Four memory channels are allocated to each processor. The allowable configurations depend on the memory mode selected. NOTE: x4 and x8 DRAM based DIMMs can be mixed providing support for RAS features. However, all guidelines for specific RAS features must be followed. x4 DRAM based DIMMs retain Single Device Data Correction (SDDC) in memory optimized (independent channel) mode. x8 DRAM based DIMMs require Advanced ECC mode to gain SDDC. The following sections provide additional slot population guidelines for each mode. 42