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)
A reader commented on a problem that end-users face when presented with HyperCloud as a solution – firstly that it is not qualified on the server that THEY use, and secondly that the HyperCloud naming/posturing is not immediately suggestive of an RDIMM-compatible product which may have made them consider it even though it was not qualified on their server.
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.
The primacy of load reduction and rank multiplication for 32GB
UPDATE: added 07/06/2012: Netlist on 8Gbit DRAM die non-availability
UPDATE: added 07/06/2012: Inphi on 8Gbit DRAM die non-availability
32GB RDIMMs are all 4-rank (quad-rank).
4-rank creates a high memory load on the memory bus.
16GB LRDIMMs vs. 16GB RDIMMs (2-rank) and 16GB HCDIMMs
16GB LRDIMMs do not outperform 16GB RDIMMs (2-rank) at 1 DPC, 2 DPC.
In addition they do not outperform the RDIMM at 3 DPC either. In contrast 16GB HyperCloud outperforms RDIMMs at 3 DPC.
Therefore, at the 16GB level, LRDIMMs:
Industry estimates of “attach rates”
UPDATE: added 06/19/2012: IDTI comments
UPDATE: added 06/22/2012: analysts on attach rates
UPDATE: added 07/03/2012: Netlist conservative $500M revenue estimate
UPDATE: added 07/03/2012: Netlist conservative $7.5B revenue estimate for 2014
UPDATE: added 07/04/2012: isuppli.com on LRDIMM market
For DDR3, load reduction is essential at:
LRDIMMs validated by JEDEC without licensing relevant IP
LRDIMMs are based on a single-sourced “iMB” buffer chipset from Inphi (more on that below).
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”.
For 32GB memory modules – the problem with 32GB RDIMMs
32GB RDIMM will only be available in 4-rank (4-rank).
For 16GB memory modules use at 1 DPC and 2 DPC
If the memory you need is going to require 1 DPC, or 2 DPC, you are better off buying the IBM RDIMMs.