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Several of Mr. Bronson's case studies are about people who found the valley's 24/7 relentlessness to be a "toxic environment." Tim Bratcher, for example, worked at Cooley Godward, one of the region's most prestigious law firms, but hated the pressures. He left Silicon Valley for Atlanta and ultimately turned to teaching law for satisfaction.

In an interview, Mr. Bronson said he found that during the boom, even though many people complained about the pace of work and the way their jobs dominated their lives, they were intoxicated by the action and left only after being laid off.

Others, like Mr. Bratcher were burned out by a corollary to the tyrannical Moore's Law: a pace of business that Intel's co-founder and chairman, Andrew S. Grove, referred to as "Internet time" in 1996, at the onset of the dot-com boom.

Dr. Moore's is not a law in the physical sense, but rather a prediction derived from the economics of the semiconductor industry. For more than three decades it has accurately predicted the accelerating power and plummeting cost of computing. Because of the exponential nature of Moore's prediction, each change has arrived faster and more furiously than the one before.

In 1968, for example, the cost of a transistor was $1. By 1995, a dollar bought about 3,000 transistors. It now fetches 50 million. Or take the clock speed of Intel's microprocessor chips, which rose gradually from about 100,000 instructions a second in 1971 to 25 million by 1989. By 2000, an Intel microprocessor was firing off 1.5 billion instructions, and now the rate is 3 billion &#0151; and climbing.

It is a business burn rate that continues to claim casualties. Recently, for example, National Semiconductor , a pioneering chip maker, said that rather than continue fighting a multifront war against obsolescence the company would sell its formerly promising information appliance business.

"Hanging in there with the products that keep chasing Moore's Law is increasingly expensive," said Brian L. Halla, National's chairman and chief executive.

Not everyone in the valley is ready yet to call time out. Those who are still thriving have little time or patience for the new wave of reflection &#0151; including Intel's Mr. Grove. Asked by e-mail message whether he had new thoughts about the meaning of Internet time, Mr. Grove issued a terse reply: "I am too busy to contemplate this."

Other executives argue that the bust simply provided a much-needed pruning of deadwood and that the valley's round-the-clock style of innovation was alive and well.

"Some people get burned out, but a lot more people come back and continue to participate in the ecosystem," said Kim Polese, co-founder and chairwoman of Marimba, a company in Mountain View, Calif., that makes software for corporate computing systems. "The valley is healthy and innovation is thriving, and we're marching forward."

Dr. Moore, for one, is standing by his principle. At the International Solid State Circuits Conference in February, Dr. Moore, who at 73 is Intel's chairman emeritus, predicted that the law would play out for another decade or so before designers reached fundamental physical limits that would prohibit the doubling of transistors in a given space.

"No physical quantity can continue to change exponentially forever," he said. But, he added, "Your job is delaying forever."

A growing number of Silicon Valley's technical experts, however, question whether Moore's Law can hold for another decade.

Each year, the Semiconductor Industry Association, which closely tracks the latest in manufacturing technology, issues a detailed International Technology Roadmap. The map is color-coded to indicate where potential challenges might develop in the future. Areas where a clear path can be seen are marked in green, and those that require more engineering in yellow. Obstacles for which there are yet work-arounds and which could stop progress entirely are marked in red &#0151; known in the chip industry as the "red brick wall."

Commenting on the latest road map at a February meeting of the International Society for Optical Engineering in Santa Clara, Calif., an I.B.M. scientist said the industry could hit a wall well before the decade was out.

William D. Hinsberg, an I.B.M. chemist at the company's Almaden Research Center in San Jose, Calif., reported that the light-resistant materials that are currently used in projecting circuit patterns onto chips may fail at dimensions below 50 nanometers. (A human hair is roughly 100,000 nanometers in width.) To keep Moore's Law on track, Mr. Hinsberg said, the industry would need to devise materials that can accommodate circuitry narrower than 50 nanometers &#0151; and would need to do so by 2007.

At the same meeting, Chris A. Mack, a vice president for lithography technology at KLA-Tencor , a company in San Jose that makes semiconductor manufacturing equipment, said in a presentation that the popular conception of Moore's Law had become outdated.

"Moore's Law is not about scaling up, it's about scaling down," Mr. Mack said in a telephone interview after his talk.

The Moore's Law race to put more transistors on a single chip is losing relevance, he said, because of limitations in the Microsoft Windows desktop computer operating system, which can process information only in 32-bit chunks and which restricts a PC's memory to four billion bytes.

If Moore's Law is reaching practical as well as physical limits, the implications could be far-reaching in Silicon Valley.

"In the future, maybe faster and cheaper would not be as important as functionality," said Doug Henton, founder and president of a Silicon Valley consulting firm, Collaborative Economics. He argues that the valley's designers and engineers took a wrong turn in adopting 24/7 lifestyles that emulated the machines they were creating.

"Productivity should be about producing more with less rather than more with more," he said.

He is far from alone in his conclusion.

"The skill sets and people's lives didn't adjust as fast as the stock market ticker," said Randy Komisar, 48, a longtime Silicon Valley executive whose credentials include tours through Apple, the Go Corporation and WebTV.

Mr. Komisar is author of a 2001 book "The Monk and the Riddle: The Art of Creating a Life While Making a Living," (Harvard Business School Press) and now works as an independent consultant &#0151; but on his own terms. He rides his motorcycle to client meetings, and he finds time most days to take a long bicycle ride in the hills above Silicon Valley.

"The ultimate question that is getting asked more and more," he said, "in a way that it wasn't being asked in 1999, is, What really matters?"