Rambus broadens memory, module bandwidth

Rambus broadens memory, module bandwidth
By Paul Kallender, EE Times
June 14, 2001 (6:37 p.m. EST)
URL: http://www.eetimes.com/story/OEG20010614S0053

TOKYO — Rambus Inc. executives this week outlined a technology road map to boost the bandwidth of the company's memory products to 9.6 Gbytes/second and to increase the width of Rambus-in-line memory modules (RIMMs) fourfold by 2005. Rambus also identified three memory makers that will support its aggressive strategy.

As the company struggles to establish its premium-priced products as mainstream memories, the Rambus road map shows Samsung Electronics Co. Ltd., Toshiba Semiconductor Co. and Elpida Memory Inc. making volume shipments of PC1066 (1,066-MHz) Rambus DRAM in 2002 and of PC1200 RDRAMs in 2005. The PC1200 version will be 50 percent faster than the PC800 parts used with today's Intel Pentium 4 microprocessor.

Rambus said it also wants to see memory makers develop 32-bit and 64-bit RIMMs, which will respectively double and quadruple the bandwidth available on current 16-bit RIMMs, the company said.

This strategy provides a si mple way of extending RIMM performance by taking advantage of RDRAM's high pin bandwidth and high granularity, said Steve Chen, vice president of partner and OEM marketing at Rambus (Los Altos, Calif.). The new RIMMs will have controller compatibility with today's 16-bit RIMMs and will quadruple performance "with minimal risk and infrastructure changes," Chen told an audience at this week's Rambus Developer Forum here.

The 32-bit RIMM will have a 232-pin connector and allow 2 to 16 devices per module, said Chen. The connector will be the same size as the existing 184-pin RIMM connectors. The 64-bit RIMM will use a 330-pin connector that is 5.25 inches wide and allow 4 to 16 devices per module. Neither of the new RIMMs will require RDRAM changes.

Rambus is attempting to build a menu of RIMM options for all market segments, from value PCs to servers, said Avo Kanadjian, the company's vice president of worldwide marketing. "Performance for desktops is doubling every three years," he said. "A way for us to stay ahead of that curve is to take our components and put them on wider modules.

"Today's PC800 and the 16-bit RIMM can go to 1.6 Gbytes/second," Kanadjian said. "The 32-bit RIMM will double that; 64-bit allows us to quadruple that. When you have faster components, you can get almost 10 Gbytes/second."

In a presentation at the forum, Rambus president David Mooring said Rambus needed to boost bandwidth to meet 10-GHz processor speeds in the middle of the decade. The strategy should also help Rambus memory populate communications applications, including the backplane interconnects for OC-192 systems targeted by the company, he said.

"We are announcing a technology that is safe, low risk and is going to allow us to take care of increasing performance," Mooring said.

Three stand ready

Samsung, Toshiba and Elpida explained how they will support Rambus' strategy in a series of statements to the press and in presentations at the forum.

Samsung plans to be the first company to sample PC1066 RDRAMs, said Jon Kang, the company's senior vice president of product planning. Samsung will produce over 130 million 128-Mbit RDRAM parts by the end of 2001, Kang said. The PC1066 RDRAM is yielding today on Samsung's 0.18-micron process, and Kang said he was confident that the yields will increase "much further" on the company's 0.15-micron technology.

A combination of factors will conspire to boost RDRAM market share next year, said Shozo Saito, general manager of Toshiba's memory division. These include the appearance of Intel's Tulloch chip set, Microsoft's Windows XP operating system, and a lessening of 256-Mbit RDRAM prices, Saito said.

Elpida is currently shipping 288-Mbit DRAMs produced in 0.18-micron technology and running at 600 MHz,700 MHz and 800 MHz, said Masaharu Yajima, expert engineer at Elpida's technical marketing division. The company will sample 288-Mbit parts produced in 0.13-micron technology first at 800-MHz and then at 1,066-MHz speeds in the first quarter of next year. Those parts will move into mass production in the second half of 2002, he said.

Yajima said Elpida will use SDRAM as a test driver to confirm the manufacturing reliability of 0.13-micron technology before moving on to the higher-bandwidth RDRAMs, which are more difficult to make and test. "SDRAM is the muscle product to develop the device and processes at this level. Then we will develop RDRAM and DDR parts," Yajima said.

Samsung could make both PC1066 and PC1200 parts much earlier than Rambus' road map suggests, said Cho Chang-Min, a sales manager at Samsung Electronics' DRAM marketing group.

"Actually, we have these speed components right now," Chang-Min told EE Times. "But no customers are interested in buying a 1,066-MHz part. They'll probably accept the 1,066 or even the 1,200 in a few years. When they do, we'll be ready. It all depends on our customers' needs."

Chang-Min said Samsung broadly accepted Mooring's contention that high-definition televisions, set-top boxes, games and switching router systems would benefit from future Rambus bandwidth. "In the long-term we are still going to support Rambus," he said. "We see many applications."

Elpida is achieving "excellent" yields on its 800-MHz RDRAM parts, said Yajima. Some believed emerging DDR chip sets from Taiwan could make a brutal cut into Rambus' planned RDRAM ramp through 2002, he said. Earlier this year Elpida announced plans to ship a cumulative 12 million RDRAM parts by the end of the year, and said it would narrow the price differentials between Rambus and DDR memories from 50 percent to under 15 percent in 2001. Elpida still believes that's doable, Yajima said.

"From the production cost point of view, the difference will become very small," he said. "But the pricing is the difference. It's a very big headache. SDRAM prices are the problem. We hope RDRAM sales for the P4 remain stable and don't fall."

RDRAM parts for the Pentium 4 are struggling against "crazy prices" for SDRAM, Chang-Min sa id. In contrast, "We have a stable, safe pricing strategy [for RDRAM]," he said.

Dealing with adversity

As memory prices continue to decline, Mooring said the PC might yet rise to Rambus' rescue. The company's four-layer motherboard lowered system costs enough for major Taiwanese motherboard makers — Abit, Acer, Asustek, Gigabyte and Microstar — to ship motherboards with Intel's 850 chip set, he said. The four-layer boards yield a 60 percent savings compared to six-layer PC boards, Mooring said.

"PC volume is the main driver. It's not growing, but it's the largest monolithic sector for some time," he said.