Supported Memory; Memory Speed; Memory Configurations And Population Rules - Dell PowerEdge R940 Technical Manual

The PowerEdge R940 supports up to 48 DIMM slots, with up to 6 TB of memory and speeds up to 2666 MT/s. Supported DIMMs are
registered (RDIMMs) and load reduced (LRDIMMs) DIMMs which uses a buffer to reduce memory loading and provide greater density
allowing maximum memory capacity.

Memory speed

The PowerEdge R940 supports memory speeds of 2666 MT/s, 2400 MT/s, and 1866 MT/s depending on the DIMM types installed and
configured. All memory on all of the processors and channels run at the same speed and voltage. The operating speed of the memory is
determined by the maximum speed supported by the processor, the speed settings in BIOS, and the operating voltage of the system.
Table 6. Memory configuration based on quantity and quality of DIMM
DIMM type DIMM ranking
RDIMM 1R/2R
LRDIMM 4R/8R

Memory configurations and population rules

The R940 supports flexible memory configurations ranging from 8 GB (minimum) to 128 GB (maximum). The R940 supports up to 12
DIMMs per processor or 24 DIMMs in a dual-processor and 48 DIMMs in a quad-processor configuration. Each R940 has 6 memory
channels per processor, with each channel supporting up to 2 DIMMs.
The R940 server support flexible memory configuration according to the following population rules:
• If DIMMs of different speeds are mixed, all channels across all processors operate at the slowest DIMM's common frequency.
• DIMM type:
• All DIMMs must be DDR4 RDIMM and LRDIMM
• Only one type of DIMM is allowed per system-RDIMM, or LRDIMM. They cannot be mixed.
• DIMMs with different data width (x4 and x8 data width) can be mixed.
• The largest DIMM capacity is placed first (slot A1 first, then A2 and so on). The second CPU mirrors the first CPU population rule.
• Maximum of two different capacity DIMMs are allowed in the system.
• Maximum of two different rank DIMMs are allowed in the system.
Table 7. DIMM mixing support
DIMM types RDIMM
RDIMM allowed
LRDIMM not allowed
3DS LRDIMM not allowed
Capacity DIMM rated voltage
and speed
8 GB, 16 GB, 32 GB DDR4 (1.2 V), 2666
MT/s
64 GB, 128 GB DDR4 (1.2 V), 2666
MT/s
LRDIMM
not allowed
allowed
not allowed

Supported Memory

Max speed (MT/s) on 1 Max speed (MT/s) on
DPC 2 DPC
2666 2666
2666 2666
3DS LRDIMM
not allowed
not allowed
allowed
Supported Memory
5
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