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Low-power DDR3-1866 LRDIMM Memory Buffer by IDT



The MB3518 is a low-power DDR3 memory buffer capable of operating speeds up to 1866 MT/s with 2 LRDIMMs in a channel. Assuming quad-rank LRDIMMs at 32 GB density, this equates to 512 GB of capacity at 1866 MT/s in a typical server, which can be doubled to over 1 TB using eight-rank 64 GB LRDIMMs, expected to launch in 2013. This represents a fourfold improvement in relative density at the highest speed grades over standard registered dual-inline memory modules (RDIMMs), enabling computing systems to support more memory and improve application performance. The memory buffer can operate at 1.5 V or 1.35 V, offering the industry’s lowest power consumption without sacrificing performance. This translates directly into huge operational cost savings for the end user in power and cooling. Presented by Doug Malech, Product Marketing Manager, Integrated Device Technology, Inc. Learn more at



My name is Douglas Malech. I’m the Product Marketing Manager for IDT’s memory-interfacing products. This presentation will concentrate on the IDT MB3518 DDR3 memory-buffer product.  The MB3518 DDR3 memory buffer is the best choice for the next LRDIMM design. It enables 1866 mega transfers per second data rates, while consuming the least amount of power of any memory buffer on the market today.
IDT is the only supplier of the memory-interfacing market space to offer leading products in every DDR generation and DIMM type. This shows our strong commitment to remain the market leader in this industry. As you can see from this table, there is no other company in the world that has a product portfolio like IDT. We’ve dedicated ourselves to this market for almost 15 years, which means every new device can leverage a very deep knowledge base. All of our competitors have gaps in their memory-interface products. Either because they are relatively new to this market, or have decided to opt out of certain device types.
LRDIMMs are used in enterprise-classed servers. Each CPU device within the server may have up to 12 DIMM memory slots associated with it. A typical enterprise-classed server may have two to four tightly-coupled CPU devices. This diagram shows two. Two to four CPUs using up to 12 DIMMs each means that a typical enterprise-classed server may have between 24 and 48 DIMM slots. Unfortunately, as speed requirements go up, the number of DIMM slots that can be populated in the system goes down. Different speed and memory densities can be realized by choosing the right RDIMM or LRDIMM solution.
LRDIMMs using IDT’S MB3518 can achieve best-industry performance at 1866 1.35v two DIMMs per channel, while providing four times the system-memory data of RDIMMs. RDIMMs can achieve one speed grade higher to 2133 speeds, but can’t compete on the system-memory densities of LRDIMMs. This table shows that at 1333 and 1600 speeds, LRDIMMs using the MB3518 can achieve the same speeds as RDIMMs while allowing three times system memory. At 1866 LRDIMMs allow four times system memory. At 2133 RDIMMs are the only choice, but the speed gap used to be a lot wider. 
Data centers today are demanding lower overall power usage to comply with green initiatives. With a typical data center containing as many as 50 thousand servers, with each server possibly containing 24 to 48 DIMMs, every watt saved per DIMM is multiplied many times over, and can potentially translate into millions of dollars of savings in operating costs. This is why power consumption is such an important parameter for today’s memory-buffer devices. The MB3518 achieves the lowest power of all memory-buffers on the market today. We compared our DDR3 memory buffer with the other competitors’ DDR memory buffers. We put each of these three buffers through the same test conditions. We measured power consumption at 1.5 and 1.35 volts, and multiple speed grades. We measured in active modes and idle modes. In all cases, the MB3518 was measured as having the lowest power consumption.
MemBIST memory built in self test, advanced air injection and reporting. Per-pin on-die oscilloscope capability, and built-in logic analyzer capability, allow intelligent access to the DRAM interface that is completely isolated from the host controller or DIMM ATE equipment. These tools allow IDT to easily report LRDIMM voltage and timing margins on the DRAM side, even though the DRAM interface is completely isolated from the host controller. As you can see from this slide, access to DRIMM DQI, and DQS strobe location within the I, are available, and are reported in an easily-readable ASCII format.
The MB3518 enables up to 1866 speeds at two DIMMs per channel. It’s designed to support next-generation, 64 gigabyte LRDIMMs. Laboratory measurements show it to be the lowest-consuming DDR3 memory buffer in the industry. It has diagnostic support to aide in debug, DIMM voltage and timing margin analysis, and other engineering-related activities. It has compliant to the JEDEC memory buffer spec, and it is manufactured and shipped by IDT, a company that has shipped about a half a billion memory-interface devices over almost 15 years.
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