Just a few years ago, OEMs evaluating flash memory for their products could choose between two competing architectures-NOR and NAND-simply by knowing whether their storage requirements were more data- or code-intensive. Those days are gone.
Changing market dynamics that demand higher-density flash devices are encouraging architectural crossovers as vendors of each specialty compete for share in emerging markets. While the majority of flash vendors are building NOR devices, shipments of NAND-based flash are expected to grow faster in the next few years.
SanDisk Corp.'s decision last month to abandon its long-held commitment to NOR in favor of NAND-based products exemplifies the changing supply landscape. Additionally, reports that Samsung Electronics Co. Ltd. and Toshiba Corp. are considering a merger of their memory divisions could concentrate vast NAND supplies under one vendor.
The market is shifting due to lower prices of flash in general, combined with the need for low-cost, high-density nonvolatile storage, according to Alan Niebel, an analyst at Web-Feet Research Inc., Mon-terey, Calif.
NOR flash can be accessed randomly and has typically been associated with code storage, or execute-in-place applications, like those found in cell phones. NAND, using sequential rather than random access, historically has been tied to applications needing large amounts of data storage, like digital cameras, MP3 players, and solid-state disk drives.
That is no longer the case. Emerging consumer products, in particular next-generation 2.5G and 3G cell phones, are slated to offer memory-intensive features such as streaming video and Internet-based data feeds, both applications that take advantage of NAND's physical makeup.
NOR or NAND?
NOR vendors, such as Advanced Micro Devices Inc. and Intel Corp., have addressed the need for higher densities by developing multilevel cell (MLC) designs that store two bits a memory cell and thus bump up density without a corresponding increase in die area or cost. These NOR devices are now used for both data/code as well as data-only storage, rendering the old measure of dividing the market along architectural lines moot.
"That was an old kind of definition, and it doesn't hold up," Niebel said.
Web-Feet recently refined its market- share projections for NAND and NOR to minimize the confusion. Basing his projections on the underlying architecture used in a system, Niebel forecasts that NAND sales will represent 9.2% of this year's $8 billion flash market.
Until recently, SanDisk, a solid-state data storage company based in Sunnyvale, Calif., had been building 256Mbit NOR-based devices using foundry sources. On Sept. 21, the company announced plans to shut down its Sunnyvale assembly plant and move entirely to a NAND-based product line.
A joint $800 million venture between SanDisk and Irvine, Calif.-based Toshiba America Electronic Components Inc., known as FlashVision LLC, began producing NAND-based flash in June at Dominion Semiconductor, a company owned by Toshiba in Manassas, Va. The partnership also extends to a Toshiba fab in Yokkaichi, Japan.
"We see a huge trend, particularly in the mobile market with emerging cell phone technology such as 2.5G and 3G, for rapidly increased storage requirements," said Bo Ericsson, vice president of OEM marketing at SanDisk. "In those markets, we believe that data storage flash [NAND] is the ideal architecture, because it's a very dense, inexpensive, high-performance technology."
Intel backs NOR
Intel, which is the leading flash vendor, contends that NOR-based devices, such as its StrataFlash product line, offer superior characteristics needed for both code and data storage applications.
"NOR is parallel and NAND is a serial architecture, so NOR is designed to be used both for embedded code and data in a system," said Scott Dunagan, flash product marketing manager at Intel, Santa Clara, Calif. "NAND is good for cards and applications like digital cameras. Our devices are more for the embedded space [like next-generation cell phones] where you want to put as much memory as you can in the device."
The NOR supply side is diversified, with Intel, AMD, and Fujitsu Ltd. controlling about half of the overall flash market in 2000, said Betsy Van Hees, an analyst at iSuppli Corp., El Segundo, Calif. Of the top 10 flash revenue producers in 2000, eight of those were primarily NOR suppliers, she said. The NAND supplier list has always been shorter and is dominated by Toshiba, Samsung, and Hitachi Ltd., which sells a similar device. Reports that Toshiba may sell its memory divisions to Samsung would create a major shift in the NAND arena, according to Van Hees.
"If they do that, it will be a huge merger in NAND," she said. "From a NAND component standpoint, they would have 80% of the market and set the market price. Samsung would also then have NOR technology to broaden its portfolio."
Even with a shift in the landscape under way, it's still a buyer's market, said Richard Doherty, an analyst at The Envisioneering Group, Seaford, N.Y. "For quick access you want NAND, for overall speed you need NOR," Doherty said. "The decision is applications driven, but key areas of discussion will be what parts are in inventory and what price accommodations can I get in the future." OR