Where are the 1600MHz LRDIMMs/HyperCloud for Romley ?

Load reduction and rank multiplication at 1600MHz ?

1600MHz-rated 16GB RDIMMs (2-rank) are available for Romley – why not LRDIMM/HyperCloud ?

The reason maybe that load reduction and rank multiplication manufacturers are already outperforming the RDIMMs by ONE speed grade.

Offering a 1600MHz version that offers a FURTHER speed grade advantage, while advantageous to end-users, may not offer a greater-units-sold advantage to the manufacturers of load reduction and rank multiplication solutions.

1600MHz memory modules require use of 1600MHz-rated DRAM memory packages.

1600MHz varieties of LRDIMM/HyperCloud ARE planned. IDTI has skipped Romley, but indicated they may have an LRDIMM available for Ivy Bridge in late 2012 addressing 1600MHz. Netlist job descriptions suggest work on 1600MHz.

So why are they not available right now ?

To understand what follows, one must first become familiar with how memory is chosen for Romley servers – i.e. when to use RDIMMs and when to use LRDIMMs/HyperCloud:

https://ddr3memory.wordpress.com/2012/06/25/memory-buying-guide-when-to-use-rdimms/
Memory buying guide – when to use RDIMMs on Romley ?
June 25, 2012

Now to examine what the availability of 1600MHz LRDIMMs/HyperCloud would add to the decision-making process outlined in the article above.

The need for 1600MHz – the 16GB case

Currently 16GB RDIMMs (2-rank) are available in 1333MHz and 1600MHz rated varieties and run at full speed at 1 DPC and 2 DPC (IBM/HP).

https://ddr3memory.wordpress.com/2012/05/24/memory-options-for-the-hp-dl360p-and-dl380p-servers-16gb-memory-modules/
Memory options for the HP DL360p and DL380p servers – 16GB memory modules
May 24, 2012

https://ddr3memory.wordpress.com/2012/05/25/memory-options-for-the-ibm-system-x3630-m4-server-16gb-memory-modules-2/
Memory options for the IBM System x3650 M4 server – 16GB memory modules
May 25, 2012

https://ddr3memory.wordpress.com/2012/05/27/what-are-ibm-hcdimms-and-hp-hdimms/
What are IBM HCDIMMs and HP HDIMMs ?
May 27, 2012

At 3 DPC, they run at 1066MHz (slowdown) – so you need a load reduction and rank multiplication type of solution.

At 3 DPC, therefore you use 16GB HyperCloud (slightly more expensive than RDIMMs).

LRDIMMs are non-viable at 16GB as they offer no speed advantage (run at 1066MHz):

https://ddr3memory.wordpress.com/2012/06/19/why-are-16gb-lrdimms-non-viable/
Why are 16GB LRDIMMs non-viable ?
June 19, 2012

At the 16GB level therefore, HyperCloud ALREADY is a speed grade faster than the default solution (RDIMMs).

If 16GB HyperCloud was to become available at 1600MHz, it would be welcomed by end-users, but may not sell any more units than the current 16GB HyperCloud.

This may be a reason why 1600MHz 16GB load reduction and rank multiplication solutions may not be available currently for Romley.

The need for 1600MHz – the 32GB case

32GB RDIMMs will be 4-rank for the foreseeable future and 4-rank experiences abysmal speed slowdown at 3 DPC and 2 DPC (actually 4-rank will not even run at 3 DPC because of the “8 ranks per memory channel” limit).

https://ddr3memory.wordpress.com/2012/05/24/memory-options-for-the-hp-dl360p-and-dl380p-servers-32gb-memory-modules/
Memory options for the HP DL360p and DL380p servers – 32GB memory modules
May 24, 2012

https://ddr3memory.wordpress.com/2012/05/25/memory-options-for-the-ibm-system-x3630-m4-server-32gb-memory-modules/
Memory options for the IBM System x3650 M4 server – 32GB memory modules
May 25, 2012

32GB RDIMMs are non-viable (for 2 DPC and 3 DPC) as examined here:

https://ddr3memory.wordpress.com/2012/06/20/non-viability-of-32gb-rdimms/
Non-viability of 32GB RDIMMs
June 20, 2012

At 2 DPC and 3 DPC you would use the 32GB HyperCloud – which would be a speed grade (or TWO) higher in speed (IBM docs show 4-rank running at 800MHz !).

This means 32GB HyperCloud delivering 1333MHz at 3 DPC is already a speed grade or two higher than what RDIMMs can deliver.

If 32GB HyperCloud was to become available at 1600MHz, it would be welcomed by end-users, but may not sell any more units than the current 32GB HyperCloud.

This may be a reason why 1600MHz 32GB load reduction and rank multiplication solutions may not be available currently for Romley.

Ivy Bridge at 1600MHz may require faster speeds

At Ivy Bridge (post-Romley) memory will be required to run at 1600MHz.

At that point it is possible that the load reduction and rank multiplication solutions may then become available at 1600MHz in order to comply with Intel PoR (“plan of record”).

Summary

This is an economic justification for WHY 1600MHz load reduction and rank multiplication (LRDIMM/HyperCloud) solutions may not be available for Romley.

One significant reason maybe that for the current market for load reduction and rank multiplication, the speed advantages of the current offerings (HyperCloud) are:

– ONE speed grade vs. 16GB RDIMMs (2-rank) at 3 DPC
.
– TWO speed grades vs. 32GB RDIMMs (4-rank) at 2 DPC (IBM docs show 4-rank running at 800MHz)
.
– Infinite speed grades higher vs. 32GB RDIMMs (4-rank) at 3 DPC (4-rank cannot run at 3 DPC !)

Offering a 1600MHz version that offers a FURTHER speed grade advantage, while advantageous to end-users, may not offer a greater-units-sold advantage to the manufacturers of load reduction and rank multiplication solutions.

This may be one reason why 1600MHz 16GB/32GB load reduction and rank multiplication solutions may not be available currently for Romley.

Postscript – faster speeds on Romley

There may of course be other issues as well – for example limitations which impede performance of 1600MHz at 3 DPC on current Romley systems.

However, the IBM x3750 M4 server has implemented some tweaks on the motherboard (which place it outside the Intel PoR) – which has the effect of improving the memory bus signal quality (on the motherboard) – this allows all memory types to experience improved performance – so both RDIMMs and LRDIMMs perform better and presumably HyperCloud would too (if available on this server). The IBM x3750 M4 server seems to be addressing the high processing power market (has high processing power/disk space ratio) and is suited for the HPC market. This is described here and also includes comments from IBM:

https://ddr3memory.wordpress.com/2012/06/02/memory-choices-for-the-ibm-system-x-x3750-m4-servers-2/
Memory choices for the IBM System X x3750 M4 servers
June 2, 2012

With this type of extra special server – where RDIMMs and LRDIMMs are able to see a ONE speed grade improvement over their regular performance on Romley servers – it is entirely possible that HyperCloud too (which already outperforms the LRDIMMs by one speed grade at 3 DPC) may also see a one speed grade improvement, i.e. from 1333MHz at 3 DPC to 1600MHz at 3 DPC.

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One response to “Where are the 1600MHz LRDIMMs/HyperCloud for Romley ?

  1. Pingback: Infographic – memory buying guide for Romley 2-socket servers | ddr3memory

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