DRAM is a popular memory technology regularly in use in almost all computers and smartphones today. However, resistive RAM or ReRAM is an upcoming parallel technology of high-density storage class memory, whose performance, researchers claim, has now reached very close to that of DRAM.
According to 4DS Memory Limited, who patented their Interface Switching ReRAM, have made substantial changes to the architecture of their product. They claim this has resulted in substantially improving read access so that the speed of ReRAM is now comparable to that of DRAMs. According to Guido Arnout, company CEO and Managing Director, the development has presented the company with several opportunities.
So far, most memory technologies have faced inherently high errors of bit rates. This includes ReRAMs as well, with randomly large cell current fluctuations to blame. Although manufacturers do include techniques for error correction to retrieve data reliably, the activity is time consuming and affects read access times negatively and cripples read speed.
After making the changes, 4DS could not find any large fluctuations with their Interface Switching ReRAM even with an extensive study. They claim this indicates the memory needs minimal error correction. Therefore, the high-density storage class memory how has effective read speeds comparable to that of DRAM. According to Arnout, the company has also scaled their memory products to 40 nm, with a significant increase in endurance.
Initially, 4DS was trying to create a storage class memory to compete with NAND flash. However, with prices of NAND flash dipping fast, the opportunity for ReRAM is now stationed between DRAM and flash. With the difference in price between DRAM and flash growing regularly, the opportunities for 4DS are also getting larger.
4DS uses a different approach for developing their Interface Switching ReRAMs. Rather than use the regular filamentary technology, 4DS uses a technique that allows cell currents to scale with geometry. According to 4DS, they use smaller cells that yield lower cell currents, and these currents can flow more reliably through narrow on-chip wires, which are necessary for achieving higher densities. However, lower cell currents also means the memory suffers longer latency, and 4DS, through extensive measurements and analysis, had to optimize the cell currents so that the latency matched that of DRAM in a high-density storage class memory.
Even short cell latency is not adequate. In reality, latency is actually made up of the sum of the inherent memory latency added to the time required to detect and correct any read errors.
The Interface Switching technology from 4DS reduces the switching region from the influence of random irregularities. That makes the latency of the new Interface Switching ReRAM the dominant factor rather than the overhead of its error correction.
SanDisk had predicted a decade earlier that ReRAM would eventually replace the NAND flash. Now, with the Interface Switching ReRAM, 4DS is looking at a tier of storage class memory that will enable data centers to deliver more content on the Internet at a faster rate and efficiency. After proving the concept of its Interface Switching ReRAM, 4DS is now focusing on scaling it for achieving decent yields.