Memory choices for SuperMicro X9 Romley servers

Absence of 1333MHz at 3 DPC – for 16GB memory modules

Like IBM and HP, SuperMicro too offers improved speeds and 1600MHz RDIMMs.

SuperMicro also supports LRDIMMs.

However, SuperMicro does not offer HyperCloud (yet).

This places SuperMicro at a competitive disadvantage in the 3 DPC segment.

That is, those servers which are going to run at full memory loading (3 DIMMs per channel) are not going to be able to run at 1333MHz at 3 DPC using HyperCloud.

But the slower 1066MHz at 3 DPC using LRDIMMs.

In addition they will be experiencing the “high latency issues” discussed elsewhere here associated with LRDIMMs.

Absence of 1333MHz at 3 DPC – for 16GB memory modules

When 32GB memory modules are required, this deficiency will get more glaring – as 32GB RDIMMs (4-rank) experience slowdown and the LRDIMMs vs. HyperCloud latency difference will figure not just at 3 DPC but at 2 DPC (since 32GB RDIMMs (4-rank) will not be in competition at 3 DPC, but also at 2 DPC and possibly 1 DPC – see IBM docs for speed slowdown for 4-rank memory).

The new SuperMicro X9 series of motherboards do not list LRDIMM support. Earlier X8 series did have LRDIM support for some motherboards (as explained elsewhere, LRDIMMs require BIOS modified before a motherboard will support LRDIMMs).

http://www.supermicro.com/products/motherboard/Xeon1333/
SuperMicro Xeon Solutions

However in feedback from SuperMicro, it seems SuperMicro IS supporting LRDIMMs for some of the X9 motherboards – however the spec sheets for those 24 DIMM (2-socket) motherboards do not explicitly mention LRDIMMs:

http://www.supermicro.com/products/motherboard/Xeon/C600/X9DRi-LN4F_.cfm
X9DRi-LN4F+

Up to 768GB DDR3 1600MHz* ECC
Registered DIMM; 24x DIMM sockets
* Depends on memory configuration

Like the HP and IBM explanations given elsewhere here, the SuperMicro servers also exhibit similar behavior with LRDIMMs.

SuperMicro guide explains how you can populate memory (see link below).

From the table one can see 4-rank experiencing severe slowdown at higher DPC (as in IBM docs):

http://www.supermicro.nl/support/resources/memory/X9_DP_memory_config.pdf
Super Micro Computer, Inc.
Memory Configuration Guide
X9 Series DP Motherboards

See pg. 4 – looking at the “DIMM slots present per CPU” = 12:

RDIMM – dual-rank (2-rank) – at 1.5V
– 1 DPC at 1600MHz
– 2 DPC at 1600MHz
– 3 DPC at 1066MHz

RDIMM – dual-rank (2-rank) – at 1.35V (low voltage)
– 1 DPC at 1333MHz
– 2 DPC at 1333MHz
– (3 DPC at 1066MH usually on IBM and HP) – SuperMicro says 3 DPC “not supported”

RDIMM – quad-rank (4-rank) – at 1.5V
– 1 DPC at 1066MHz
– 2 DPC at 800MHz
– 3 DPC not supported (because 4 ranks x 3 DPC = 12 ranks which exceeds the 8 ranks per memory rank limit of current systems)

RDIMM – quad-rank (4-rank) – at 1.35V (low voltage)
– 1 DPC at 800Hz
– 2 DPC at 800MHz
– 3 DPC not supported (because 4 ranks x 3 DPC = 12 ranks which exceeds the 8 ranks per memory rank limit of current systems)

LRDIMM (4-rank) – at 1.5V
– 1 DPC at 1333MHz
– 2 DPC at 1333MHz
– 3 DPC at 1066MHz

LRDIMM (4-rank) – at 1.35V (low voltage)
– 1 DPC at 1333MHz
– 2 DPC at 1066MHz
– 3 DPC at 1066MHz

Which places them at a competitive disadvantage to IBM and HP who deliver HyperCloud:

HCDIMM – at 1.5V
– 1 DPC at 1333MHz at 1.5V
– 2 DPC at 1333MHz at 1.5V
– 3 DPC at 1333MHz at 1.5V

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