Memory bottleneck targeted -- Industry Works On Speeding Up Transfer Rates
Paul Korzeniowski
New York -- Improved memory interfaces are on the horizon but will not reach shore for another 18 to 24 months. The arrival will provide resellers of PCs, servers and workstations with new revenue opportunities, but it also will mean that they have to carry more inventory and provide more customer support.
The need for improved memory interfaces stems from rapid, ongoing improvements in microprocessors. "While microprocessor performance has increased 200 times during the past 10 years, memory speeds have only grown by a factor of 20," said Gregg Bouchard, programming engineer at Compaq Computer Corp.'s Alpha Development Group in Shrewsbury, Mass.
Consequently, internal memory speed has become a bottleneck in users' never-ending quest for faster computers. Cognizant of the problem, Intel Corp., Santa Clara, Calif., began working with Rambus Inc., Mountain View, Calif., in December 1996 to speed up memory transfer rates to 1.6 Gbytes per second.
Delivering such a significant performance boost is no minor engineering feat. Subodh Toprani, vice president and general manager at Rambus, said the company had to develop new signaling techniques and lower the voltage transferred whenever bits change.
As Direct Rambus matures, it is expected to make its way into the mass market. "One of the attractions to working with Intel is its ability to expand use of complex technology," Toprani said.
The transition is expected to be slow. The high-speed memory system is expected to be found in high-end workstations in 1999, midrange systems in 2000 and sub-$1,000 PCs in 2001.
Competing techniques for speeding up memory-SLDRAM and Double Data Rate DRAM (DDR DRAM)-also are vying for attention. Two versions of SLDRAM are being touted.
SLDRAM I, with a top memory transfer rate of 600 Mbytes per second, is being pitched as a low-cost follow-on to existing main memory. SLDRAM II will be based on the chip design of SLDRAM I, but with modifications that will enable a memory transfer rate of 1 GBps.
Initially, PC vendors will find it cost-effective to use SLDRAM I instead of Direct Rambus DRAM, said Farhad Tabrizi, president of SLDRAM Inc., an industry group promoting the standard, and director of worldwide marketing for Hyundai Electronics America's semiconductor division.
The target market for SLDRAM is servers and workstations. The performance of a majority of memory interfaces and chipset controllers used in those products is not dictated by Intel. Companies supporting SLDRAM include Micron Technology Inc. and Siemens AG.
Although Direct Rambus is being designed into high-end systems from companies such as Dell Computer Corp., Austin, Texas, and Digital Equipment Corp, Maynard, Mass., Tabrizi said SLDRAM's chief competitor in the server/workstation market will come from the industry's other emerging DRAM alternative: DDR SDRAM.
Samsung Semicondutor Inc. has been the main backer of the DDR SDRAM approach. Cyrix Corp., Richardson, Texas, and Fujitsu Microelectronics Inc. have stated their intentions to deliver related products.
With the exception of Micron's PC unit, no major PC supplier has revealed plans to incorporate a non-Rambus DRAM technique into its products, said James Handy, industry analyst at Dataquest, San Jose, Calif.
Last month SLDRAM and DDR SDRAM lined up against each other to seek the endorsement of an ad hoc industry consortium, the Server DRAM Forum, whose task is to recommend a single wideband architecture that will carry through three generations of high-speed memory chips.
Compaq's Bouchard said the company examined all the possible memory improvement options earlier this year and opted for Direct Rambus. "The alternatives didn't offer as much speed or have the backing from the main players, such as Intel, that Direct Rambus does," he said.
Also planning to support the Direct Rambus specification are connector manufacturer Berg Electronics Inc., St. Louis; clock chip makers Cypress Semiconductor Corp., San Jose, Calif., and International Microcircuits Inc., Milpitas, Calif.; and semiconductor test-equipment vendors Advantest Corp., Tokyo, and Hewlett-Packard Co., Palo Alto, Calif.
When these vendors ship their wares, PC manufacturers and resellers can incorporate them into new or existing systems for customers. Although no vendor has given shipment dates, Compaq, Houston, and Dell have stated plans to deliver systems compliant with Direct Rambus next year.
Initially, use of the improved internal memory is expected to be limited. "The Direct Rambus feature will start off first in high-end workstations and servers, products where customers can justify paying for the extra horsepower," Handy said.
The initial wave of compliant products is expected to cost twice as much current components. While resellers could make a dollar or two selling the high-performance memory, they also will face increased costs.
"Resellers will have to carry inventory for current memory systems, as well as for the new technique," Handy said. Customers may be confused about the benefits afforded by the faster memory, and that could increase support costs, he said.
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