Fujitsu PRIMERGY TX2550 M5 Upgrade And Maintenance Manual page 398

Main memory
Independent Channel mode with different DIMMs
– Same letter represents identical DIMMs (capacity, rank).
– If using two different DIMMs, use a "near-balanced" platform configuration:
– all available memory channels and sockets populated equally
– identical DIMMs in each "row", but different sized DIMMs in row #1 and
row #2
– 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.
– Same quantity of both DIMMs are required on each CPU.
– "x" must always be DIMM with more ranks than "z".
– If both DIMMs have same number of ranks, "x" represents DIMMs with
higher capacity.
Mirrored Channel mode
– Same letter represents identical DIMMs (capacity, rank).
– Channels 1A/1B/1C must be populated with identical DIMMs.
– Channels D-F must be populated accordingly.
398 Upgrade and Maintenance Manual TX2550 M5