3GHz PowerPC G5 Eludes IBM

IBM's difficulties raising the speed of its PowerPC 970 CPU and other 90nm process products has frustrated key customers, such as Apple and Nvidia.

Even the most ingenious chip designs can be undone by manufacturing problems: Consider IBM Corp.s struggle to raise the megahertz ante for its PowerPC processors.

The company has managed to keep delivering chips without major interruptions. Nevertheless, issues with two of its key clients point at problems manufacturing its chips at their rated speeds. The PowerPC chips that IBM supplies to Apple Computer Inc. are slower than Apple expected, and Nvidia Corp.s GeForce 6800 card has yet to ship in appreciable quantities.

For its part, Somers, N.Y.-based IBM claims that it has weathered the transition from 130-nm to 90-nm as well as its competitors. Thats at least partially true, even if its faint praise: Advanced Micro Devices Inc., Intel Corp. and foundries such as Taiwan Semiconductor Manufacturing Co. have all stumbled during transitions to new process technologies.

/zimages/5/28571.gifSpeaking of stumbles, Intel recalled more than 100,000 of its Grantsdale chipsets only days after their release. Click here to read more.

However, on June 23, 2003, Apple CEO Steve Jobs told a crowd at its Worldwide Developers Conference in San Francisco that the company would be shipping 3GHz PowerPC desktops within 12 months. "Its a fantastic architecture, and its got legs," Jobs said at the time. Its now a year later, and Apples fastest G5 desktops run at only 2.5GHz.

So far, most of the discussions with IBMs fab have dealt with the "defect density," the number of devices on the wafer that actually work. But as Apples case points out, the issue may also be with IBMs ability to "speed-bin" chips to meet its customers demands.

A semiconductor fabs output is rated according to "yield," which usually means the number of functional processors contained on the silicon wafer. If a chip fails to operate, it cant be sold. But a chip that fails to operate at a rated speed may also be a wasted effort, if a customer is positioning a microprocessor or other chip against a competitor.

"The issue today in most modern fabs is not whether it works or not but whether it yields effectively at a marketable speed," said Nathan Brookwood, an analyst at Insight64 in Saratoga, Calif.

/zimages/5/28571.gifIBM is also addressing mobility with a new power-saving architecture. Click here to read more.

IBMs yields are, of course, a secret, and IBM executives declined to divulge specifics. "I dont believe IBM made that prediction publicly," said Jesse Stein, IBMs PowerPC marketing programs manager, of the 3GHz prediction actually made by Jobs.

"Were ahead of our competition, although I dont want to disparage anybody," Stein added. "The frequency jumps weve been able to achieve with the [PowerPC] 970FX have been greater than some of our competitors from 130 nm to 90 nm. Were getting a larger frequency jump, and were facing the challenges better than most."

John Kelly, senior vice president and group executive for technology in IBMs Systems & Technology Group, acknowledged the defect issue in a conference call with reporters in May. "As our CFO John Joyce said when we reported our first-quarter earnings, our 200-millimeter yields are basically at or above our plan while our 300-millimeter yields have been improving but are not quite yet where we want them to be," he said.

Kelly said the companys 130-nm, 300-mm defect densities are "showing rapid improvement." About 50 percent of the companys manufacturing is at 130-nm processes or smaller, he said. "Finally, as John Joyce suggested, we expect to do a better job of meeting our customer demand in the second quarter," Kelly said.

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