Tag Archives: RDIMM

Awaiting 32GB HCDIMMs

Industry needs availability on a wide range of servers

When 32GB HCDIMMs become available, they will be the memory module of choice in the 32GB segment.

This will be applicable to both the regular Romley servers as well as the non-Intel-POR (plan-of-record) servers like the IBM x3750 M4 server.

The reason is that:

– HCDIMMs are RDIMM-compatible
– HCDIMMs run at higher speed than LRDIMMs
– HCDIMMs outperform LRDIMMs in latency and throughput even when HCDIMMs are run at the lower same speeds as LRDIMM

Their qualification on a wide range of servers is essential for the industry to get access to the best memory available.

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Latency and throughput figures for LRDIMMs emerge

LRDIMMs exhibit 45% worse latency and 36.7% worse throughput at 3 DPC

LRDIMMs (which are a new standard and incompatible with DDR3 RDIMMs) exhibit significant performance impairment at 3 DPC compared to RDIMM-compatible HCDIMMs:

– LRDIMMs have 45% worse latency than HCDIMMs (235ns vs. 161.9ns for HCDIMMs)
– LRDIMMs have 36.7% worse throughput than HCDIMMs (40.4GB/s vs. 63.9GB/s for HCDIMMs)

And this is when HCDIMMs are run at a SLOWED down 1066MHz at 3 DPC (in order to match the lower max achievable speed of the LRDIMMs).

This comparison – at SAME speed – highlights the architectural weaknesses of the LRDIMM design irrespective of the speeds.

When compared at the MAXIMUM achievable speeds (LRDIMMs at 1066MHz at 3 DPC and HCDIMM at 1333MHz at 3 DPC):

– LRDIMMs have approx. 45% worse latency than HCDIMMs (235ns vs. 161.9ns for HCDIMMs)
– LRDIMMs have 40% worse throughput than HCDIMMs (40.4GB/s vs. 68.1GB/s for HCDIMMs)

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HyperCloud to own the 32GB market ?

Marketability as a better RDIMM

UPDATE: 07/09/2012 – buyout
UPDATE: 07/09/2012 – strategic value of RDIMM-compatibility and misconceptions debunked
UPDATE: 07/27/2012 – confirmed HCDIMM similar latency as RDIMMs
UPDATE: 07/27/2012 – confirmed LRDIMM latency and throughput weakness

Is Netlist a buyout candidate ?

Is LRDIMM a dead-end product ?

Is it easier to market a better RDIMM that includes all the features of an LRDIMM ?

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VLP RDIMMs for virtualization on Blade Servers

Why Netlist 16GB VLP RDIMM outperforms the competition

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

Netlist claims their 16GB VLP RDIMM has improved performance and reliability/robustness vs. the competitors’ products. And is also cheaper to make.

VMware has certified Netlist 16GB VLP RDIMM memory modules for use with VMware products – it is the only VLP memory product certified by VMware.

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Memory for VMware virtualization servers

VMware certification limited to Netlist HyperCloud and VLP only

Netlist becomes the only memory certified by VMware on it’s virtualization products.

I cannot find a VMware testimonial in favor of LRDIMMs.

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Examining LRDIMMs

LRDIMMs vs. the RDIMM standard

UPDATE: 07/06/2012 – VMware certifies Netlist as sole memory vendor
UPDATE: 07/27/2012 – confirmed HCDIMM similar latency as RDIMMs
UPDATE: 07/27/2012 – confirmed LRDIMM latency and throughput weakness

Load Reduced DIMMs (LRDIMMs) are a new JEDEC-ratified standard for memory modules.

The key difference between RDIMMs and LRDIMMs is load reduction and rank multiplication capability.

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Multi-die vs. multi-PCB to increase memory density

Netlist Planar-X – cheaper 32GB RDIMMs and VLP

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

With increasing memory capacity, there is a need to fit a greater number of memory packages (which hold the DRAM die) onto the limited space on a memory module.

One way is to minimize the number of memory packages – by fitting more DRAM dies in a memory package (multi-die).

The other is the increase the real-estate by using a sandwich of multiple PCBs to build the memory module (multi-PCB).

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