See the requirement for an Intel Server Board like S5520UR for example:
It says clearly that mixing memory with different sizes, type, speed has not been tested, validated:
Note The following configurations are not validated, supported, or recommended:
- Mixing of RDIMMs and UDIMMs
- Mixing memory type, size, speed, and/or rank
- Mixing memory vendors
- Non-ECC memory
If someone else has tried this, may be they can help you or give you some more information.
All the best,
In addition to that,
Follow these rules for peak performance:
• Always populate both processors with equal amounts of memory to ensure a balanced
• Always populate all 3 memory channels on each processor with equal memory capacity.
• Ensure an even number of ranks are populated per channel.
• Use dual-rank DIMMs whenever appropriate.
• For optimal 1333MHz performance, populate 6 dual-rank DIMMs (3 per processor).
• For optimal 1066MHz performance, populate 12 dual-rank DIMMs (6 per processor).
• For optimal 800MHz performance with high DIMM counts:
– On 12 DIMM platforms, populate 12 dual-rank or quad-rank DIMMs (6 ) per processor.
– On 16 DIMM platforms:
_ Populate 12 dual-rank or quad-rank DIMMs (6 per processor).
_ Populate 14 dual-rank DIMMs of one size and 2 dual-rank DIMMs of double the size
as described in the interleaving section.
• With the above rules, it is not possible to have a performance-optimized system with 4GB,
8GB, 16GB, or 128GB. With 3 memory channels and interleaving rules, customers need to configure systems with 6GB, 12GB, 18GB, 24GB, 48GB, 72GB, 96GB, etc., for optimized