eetimes article on GHZ+ processors (thanks to AMDZone for the link)
eet.com
ISSCC: Processors gallop past the GHz mark
By Will Wade
EE Times
(02/09/00, 6:23 p.m. EST)
SAN FRANCISCO?The four heavy hitters in processor design surged past the GHz barrier with architectural modifications shown at ISSCC here, but the breakthroughs are more symbolic than significant for end-applications performance, observers said.
Intel Corp., IBM Corp., Compaq Computer Corp. and Advanced Micro Devices Inc. all showed designs or demonstrated devices that crack the magic GHz barrier; some of them are expected to be turned into commercial products this year.
"There is nothing magic about running at a gigahertz," said Keith Diefendorff, editor-in-chief for Microprocessor Report (Sunnyvale, Calif.). "It is certainly a goal that people have been striving for, but running at 1 GHz is no different from running at 999 MHz."
That doesn't mean the efforts of chip designers have been wasted. Software designers always will find ways to use the extra power available to them, Diefendorff said, adding that one simple use is to improve applications that already exist.
"There are plenty of applications that use all the horsepower you can throw at them," he said. "With more power, we won't necessarily see new and revolutionary applications, but we might start to see some that work right."
This could eventually include such basic features as the grammar checker on word processors, or better video and audio editing capabilities. All of these exist now, but need far more artificial intelligence to really work well, and that will demand processors significantly more advanced than even the high-speed chips shown at the ISSCC event.
Intel delivered a paper on a 1 GHz version of its current Coppermine product. It uses the company's 0.18-micron process and continues to use all-aluminum interconnect. Peter Green, design manager for Intel, said there are few architectural advances over the current 800 MHz Coppermine products that are commercially available. It does feature an on-die Level 2 cache that runs at the same frequency as the processor core, and the design has been modified to decrease latency.
The aluminum interconnect is paired with low-K dielectric material, and the wires themselves have large aspect ratios. "This is not a stunt," said Green. "A gigahertz design brings tangible performance increases to the user. You can see it and feel it." Green said the 1 GHz Coppermine will be available commercially before the end of the year.
Not to be outdone, Intel's processor rival AMD demonstrated at the conference a 1.116 GHz version of its Athlon processor. While the Coppermine continues to use the same Pentium core that has been the mainstay of Intel's product line for several years, the Athlon uses a completely new design that was introduced last year. Diefendorff said the design likely will have more headroom for speed increases than the Coppermine. However, Intel will also bring out a new core this year, the Willamette.
AMD did not deliver a paper at ISSCC, but did bring along a system to show off the speedy Athlon. The chip featured all-copper interconnect, a 0.18-micron process and an on-die Level 2 cache. It was produced at the company's new fab in Dresden, Germany. A company spokesman said that AMD will implement both copper interconnect and on-die cache designs into its product line over the next two quarters. The 1.1 GHz chip should be available in the fourth quarter, although he would not confirm that the commercial version would use either or both of those architectural improvements.
Diefendorff said that chips aimed at mainstream PC marketplace would almost certainly see the highest sales volume of all the high-speed devices unveiled at ISSCC. However, that doesn't necessarily make them the best design. He said the new 64-bit PowerPC design from IBM was an impressive feat because it coaxed 1 GHz out of a very short pipeline.
"Most of the complexity in microprocessors today comes from the problems of having very long pipelines to generate high-frequencies," he said. "A short pipeline is more efficient."
The IBM team used a four-stage design, along with copper interconnect and a 0.22-micron process. "Traditionally, one of the ways to improve performance in a processor is to add pipeline stages, so the amount of work done per cycle goes down," said Peter Hofstee, from the IBM research lab in Austin, Texas. "We have improved cycle time by requiring harder work in all pipeline stages, so this design is well-balanced," he said.
The chip delivers peak performance of 1.2 GHz, but that drove the operating temperature up to 125 degrees C. Diefendorff said this project was more of a research experiment, and it was not likely to see any commercial applications.
The final entry in the GHz class was an Alpha chip from Compaq's Alpha Processor Inc. subsidiary. It was built with seven layers of aluminum interconnect with a 0.18-micron process, and low-K dielectric material, and is designed for both standard wirebond and flip-chip packaging. Bradley Benschneider, senior member of the technical staff at Compaq, said that performance will jump with the flip-chip architecture by as much as 10 percent, and that the device ran at 1.65 volts.
Diefendorff said that Alpha design has always been know for high-speed, but that it has achieved very little market presence. Compaq is the only significant OEM to use the chips in their servers, and he predicted that even Compaq will switch to Intel chips once its 64-bit processors become available later this year. "I can't imagine that Compaq will continue to carry the architecture forward," he said. |
