Monthly Archives: May 2012

Memory choices for Cisco UCS B200 M3 Blade Server (Romley)

This server has 24 DIMM slots for a total of 384GB (using 16GB RDIMMs).

However I cannot find any docs outlining the speeds achievable at 1 DPC, 2 DPC, 3 DPC (as are available from IBM and others).

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LRDIMM latency vs. DDR4

UPDATE: 06/24/2012: Invensas on LRDIMM design inferiority vs. HyperCloud
UPDATE: 07/27/2012 – confirmed HCDIMM similar latency as RDIMMs
UPDATE: 07/27/2012 – confirmed LRDIMM latency and throughput weakness

RDIMMs have a 1 cycle latency compared to UDIMMs (unregistered DIMMs).

LRDIMMs have a “5 ns latency penalty” compared to RDIMMs (from Inphi LRDIMM blog).

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LRDIMMs similarities with MetaRAM

Patent reexamination as a double-edged sword

UPDATE: added 06/24/2012: Invensas on LRDIMM design inferiority vs. HyperCloud

Some years ago MetaRAM arrived on the scene. It had the support of Intel (see link below) and some significant venture backing (Intel VC, Khosla Ventures).

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What are IBM HCDIMMs and HP HDIMMs ?

Comparing RDIMMs, LRDIMMs and HCDIMMs/HDIMMs

UPDATE: 07/06/2012 – VMware certifies Netlist as sole memory vendor

Adding this as an entry point (or crash course) for folks asking about HCDIMMs and HDIMMs on twitter.

IBM HCDIMMs are Netlist HyperCloud.

HP HDIMMs are Netlist HyperCloud (called “HP Smart Memory HyperCloud”).

HP Smart Memory includes some other diagnostic/error features, and so that feature set has been extended to the HyperCloud and it is therefore also called a “HP Smart Memory”.

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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).

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Memory choices for Dell 12G Romley servers

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

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

Dell also supports LRDIMMs.

However, Dell does not offer HyperCloud (yet).

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Memory options for the IBM System x3650 M4 server – 32GB memory modules

For 32GB memory modules – the problem with 32GB RDIMMs

32GB RDIMM will only be available in 4-rank (4-rank).

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