Modes Of Operation; Ddr4 Dimm - Fujitsu PRIMERGY RX2520 M5 Upgrade And Maintenance Manual

Main memory
– Mixing of non-3DS and 3DS LRDIMMs is not allowed per platform.
– DIMMs with different frequencies can be mixed in the system, but lowest
frequency determines the system memory speed.
– There should be at least one DDR4 DIMM per CPU socket (slot 1A/1G).
10.2.3

Modes of operation

10.2.3.1

DDR4 DIMM

Three different memory RAS modes are supported (Lockstep Channel mode is
not supported):
– Independent Channel mode
– Rank Sparing mode
– Mirrored Channel mode
Below are the system level RAS mode combination limitations:
– Mixing of Independent Channel mode and Lockstep Channel mode is not
allowed.
– Mixing of Non-Mirrored and Mirrored Channel mode is not allowed.
– Mixing of Lockstep mode and Mirrored Channel mode is not allowed.
– Mixing of Rank Sparing mode and Mirrored Channel mode is not allowed.
Independent Channel mode with identical DIMMs
– Same letter represents identical DIMMs (capacity, rank).
– Use a "balanced" platform configuration:
– all available memory channels populated equally
– identical DIMMs in all locations (size/speed/rank)
– Marked (*) quantity of DIMMs are not recommended because of unbalanced
configurations.
– Unbalanced configurations can lead to significantly reduced bandwidth
because the system will fracture the memory space into multiple regions.
260 Upgrade and Maintenance Manual RX2520 M5