The good old days for SRAMs appear to be over.

About eight years ago, demand for SRAMs was strong as cell phones gobbled up 4 megabit (Mb) and 8Mb devices. Today phones need a lot more memory, but cost is more of a concern so cell phone OEMs are equipping handsets with less costly DRAM instead of SRAM.

The result is a declining SRAM market. SRAM revenue totaled about $2.4 billion in 2007, but will drop to $1.5 billion in 2011, according to Semico Research Corp. in Phoenix. The good news for buyers is prices will continue to fall as well. For example, the average price of a synchronous DRAM will fall from $12.01 in 2007 to $11.20 in 2011, the researcher says.

SRAMs remain popular in some niche markets. For example, Chatsworth, Calif.-based Aitech Defense Systems, which manufactures rugged computer systems for use in harsh environments, purchases four different types of SRAM, says Danny Crabb, a senior buyer at Aitech. SRAMs are used in processor and communications input/output cards. They are also used in networking and communications equipment which require fast memories. However, overall there will be less demand for SRAMs.

"The industry-wide decline in demand for SRAMs can be attributed to further market evolution toward DRAMs," says Kevin Lee, vice president of memory marketing at Samsung Semiconductor in San Jose, Calif. Pricing and availability are both stable, Lee contends, adding that speeds are improving incrementally, from 300MHz to 400MHz, and densities are hovering around 72Mb.

"The SRAM market has lost some market share to other solutions in recent years, but continues to be a viable market for us," Lee says.? "We have a lot of resources aimed at continuing to meet SRAM demand and maintaining our number-one market position because we believe that SRAM will remain a viable market."

The SRAM market is diverse. Samsung manufactures synchronous SRAM products including 300MHz quad data rate (QDR) and 250MHz NtRAM (no-turnaround random access memory) devices at its plant in Hwasung, Korea. Cypress Semiconductor targets networking applications with high-speed synchronous SRAMs in 1Mb to 72Mb densities. Its asynchronous SRAMs are available in 4Kb to 32Mb densities, largely for use in switches and routers. Toshiba and Micron, however, both focus on pseudo SRAMs (PSRAMs), which are essentially DRAMs with an SRAM interface. Toshiba combines PSRAMs with NAND or NOR flash memory in multichip packages (MCP).

"PSRAMs marry up well with NOR flash devices in cell phones," says John Schreck, vice president of DRAM development at Micron Technology, based in Boise, Idaho. "As long as NOR flash is important, then PSRAMs will be there with it."

As logic chips are fabricated on smaller geometries, SRAM can be embedded on microcontrollers, which makes access times faster, says Mark DeVoss, senior analyst for memory devices at researcher iSuppli in El Segundo, Calif. Sockets for discrete SRAMs are lost as more SRAM is embedded. As densities of discrete devices increase from 9Mb to 18Mb, 36Mb, and 72Mb, the smaller densities collapse, he says. Slower SRAM devices are the most vulnerable to replacement. Fast SRAMs remain attractive for use in packet processing lookup tables, according to DeVoss.

"What's driving the requirement for speed in those (packet switching) applications are the ASICs (application specific integrated circuits) they're connected to," says Rob Raghavan, marketing manager for Renesas Technology America's custom LSI business unit in San Jose, Calif. "ASICs are in the 300MHz frequency range and below, but that's changing. They will go up to the 500MHz level." QDR2 (quad data rate) SRAMs operate at up to 333MHz, QDR2+ at up to 500MHz.

Renesas currently offers a 36Mb QDR2 SRAM, but Raghavan sees a ramp-up to 72Mb as early as the first half of next year. "The demise of SRAMs is greatly exaggerated," he says.