Static RAM computer memory (SRAM) is a niche memory market, but still a critical one, and it is unlikely to be supplanted anytime soon by another technology, given its unmatched performance and speed capabilities for certain applications.
Networking is one area where SRAM continues to excel as Internet traffic continues to grow exponentially and network infrastructures must continue to upgrade in order to handle moving and storing more data. The 100 to 400 Gigabit linecards found in next-generation switches and routers are hungry for memory that can support the random transaction rates (RTRs) found in network traffic today. An RTR is the number of fully random memory accesses per second, and a critical memory performance metric for increased linecard and switching rates.
While SRAM has its uses in other applications, Quad Data Rate IV (QDR-IV) SRAM was designed for high-speed communications and networking applications, and it prioritizes data throughput over cost, power efficiency, or density, unlike DRAM or flash. At the same time, the goal is also to double performance of SRAM with each generation.
“The network and telecom market is definitely driving the SRAM definitions right now,” says Bob Haig, marketing manager at GSI Technology, an SRAM-focused vendor. As network gear has moved to 400G linecards, the demand for SRAM bandwidth has scaled right along with it.
Other applications for SRAM include military hardware and medical devices. But compared to the DRAM segment, SRAM is much smaller, with few players. “The market has become more and more specialized,” Haig tells us. “There is no longer one type of device that serves everyone’s needs.”
GSI has a large catalogue of SRAM offerings, but Haig says other memory players have exited the space because, unlike DRAM, which has fewer products sold at high volumes, SRAM has a lot of different products sold at low volumes.
Meanwhile, Cypress Semiconductor Corp., a significant player in the SRAM market, just introduced QDR-IV SRAMs in 144 and 72 megabit densities to support the RTRs required for 100 to 400 gigabit linecards in next-generation switches and routers. Sudhir Gopalswamy, senior director of Cypress’s SRAM business unit, says the bottleneck for reaching increased linecard rates is the processing of lookup tables, statistics, and state counters stored in memory, as well as scheduling functions.
Cypress also offers a broad array of SRAM across different categories. Gopalswamy says QDR-IV has been addressing the networking segment for some time, and although some gear does use DRAM for some tasks, it’s not going to work for lookup functions and statistics management. “You just don’t have the random transaction rate performance.” Some high-performance-computing and military applications, such as radar, also require the RTR performance of QDR-IV.
Haig says GSI will have a 288 megabit QDR-IV offering later this year. The company also offers reduced latency DRAM (RLDRAM), which is a low-latency, high-bandwidth DRAM designed for networking and Layer 3 caching and outperforms DRAM, yet still does not provide the performance of SRAM. Other vendors that produce RLDRAM include Micron.
SRAM will continue to have a strong, if smaller, market, says Gopalswamy, because there is no end in to the doubling of network traffic. “Equipment providers are doubling their packet rate capacity every 18 to 24 months.”
Jim Handy, principal at Objective Analysis, says at the moment there is nothing that can match the performance of SRAM for networking equipment, especially as it evolves to faster speeds. “SRAM can process the lookup tables that you need for networking faster than any other technology.”
He says SRAM will continue to be a niche market, unlike DRAM and NAND Flash, and an expensive memory, much like the linecards used in networking gear where SRAM is used. “Everyone has to use the same SRAMs and the same processors.”
Handy adds there has been some discussion that Hybrid Memory Cube, one of the likely long-term replacements for DRAM, might be able to offer some of the same functions as SRAM, but there would likely be some compromises in performance.