Dell EMC PowerEdge R7425 Installation and Service Manual

The 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 installing memory modules:

• All DIMMs must be DDR4.
• RDIMMs and LRDIMMs must not be mixed.
• x4 and x8 DRAM based memory modules can be mixed.
• 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.
• A maximum of two different ranked DIMMs can be populated in a 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).
• Populate memory module sockets only if a processor is installed.
  • For single-processor systems, sockets A1 to A16 are available.
  • For dual-processor systems, sockets A1 to A16 and sockets B1 to B16 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 the highest capacity first.

  For example, if you want to mix 8 GB and 16 GB memory modules for one DIMM per channel, populate 16 GB memory modules in the sockets with white release tabs (A1,A2,...A8) and 8 GB memory modules in the sockets with black release tabs (A9,A10,....A16).

• Memory modules of different capacities can be mixed provided other memory population rules are followed.

  For example, 8 GB and 16 GB memory modules can be mixed, provided they are in different channels.

• In a dual-processor configuration, the memory configuration for each processor must be identical.

  For example, if you populate socket A1 for processor 1, then populate socket B1 for processor 2, and so on.

• Mixing of more than two memory module capacities in a system is not supported.
• Unbalanced memory configurations will result in a performance loss so always populate memory channels identically with identical DIMMs for best performance.
• Populate eight identical memory modules per processor (one DIMM per channel) at a time to maximize performance.
• To ensure proper cooling in the system with mid-backplane, memory module blanks must be installed in memory sockets that are not occupied.