Dell PowerEdge XE9780 Installation and Service Manual
General memory module installation guidelines
To ensure optimal performance of your system, observe the following general guidelines when configuring your system memory. If your system's memory configuration fails to observe these guidelines, your system might not boot, stop responding during memory configuration, or operate with reduced memory.
The memory bus may operate at speeds of 6400 MT/s depending on the following factors:
- System profile selected (for example, Performance, Performance Per Watt Optimized (OS), or Custom [can be run at high speed or lower])
- Maximum supported DIMM speed of the processors
- Maximum supported speed of the DIMMs
NOTE: MT/s indicates DIMM speed in MegaTransfers per second.
The following are the recommended guidelines for installing memory modules:
- All DIMMs must be DDR5.
- All DIMMs in a channel must have the same number of ranks.
- x8 DIMMs x4 DIMMS cannot be mixed in the same channel or same processor socket.
- Nine x4 RDIMMs cannot be mixed with other DIMMs.
- Rank mixing is not allowed on a channel except for 1 rank + 2 rank combination, when all 16 DIMM are populated for a processor socket.
- Mixing of non-3DS and 3DS RDIMMs is not allowed in the same channel, across different channels, and across different sockets.
- Density mixing is not allowed.
- Frequency mixing is not allowed.
- Mixing vendor is allowed for both RDIMM and 3DS RDIMM.
- When one DIMM is used in a channel, it must be populated in DIMM slot farthest away from the CPU (DIMM slot 0) of a given channel.
- If memory modules with different speeds are installed, they operate at the speed of one or more slowest installed memory modules.
- A maximum of eight logical ranks (ranks seen by the host) per channel is allowed.
- Populate memory module sockets only if a processor is installed.
- For dual-processor systems, sockets A1 to A16 and sockets B1 to B16 are available.
- In
Optimizer Mode, the DRAM controllers operate independently in the 64-bit mode and provide optimized memory performance.
Table 1. Memory population rulesThe below table describes the memory population information. Processor Memory population Memory population information Dual processor (Start with processor 0. Processor 0 and processor 1 population should match) A{1}, B{1}, A{2}, B{2}, A{3},B{3}, A{4}, B{4}, A{5}, B{5},A{6}, B{6}, A{7}, B{7} A{8},B{8}, A{9}, B{9}, A{10},B{10}, A{11}, B{11}, A{12}, B{12}, A{13}, B{13}, A{14},B{14}, A{15}, B{15}, A{16},B{16} 16 or 32 DIMMs are supported per system. - Populate all the sockets with white release tabs first, followed by the sockets with black release tabs.
- Mixing of any different memory module capacities is not supported.
- Supported RDIMM configurations are 8 or 16 DIMMs per processor.
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