AN FRANCISCO, June 1 — For almost two decades the federal government has heavily underwritten elaborate centers to house the world's fastest supercomputers. The policy has been based on the assumption that only government money could ensure that the nation's research scientists had the computing power they needed to pursue projects like simulating the flow of air around a jet airplane wing, mimicking the way proteins are folded inside cells or modeling the global climate.

But now two leading American computer researchers are challenging that policy. They argue that federal money would be better spent directly on the scientific research teams that are the largest users of supercomputers, by shifting the financing to vast data-storage systems instead of building ultrafast computers.

Innovation in data-storage technology is now significantly outpacing progress in computer processing power, they say, heralding a new era where vast pools of digital data are becoming the most crucial element in scientific research.

The researchers, Gordon Bell and Jim Gray, scientists at Microsoft's Bay Area Research Center, presented the argument last month in a meeting of the National Research Council's Computer Science and Telecommunications Board at Stanford University.

"Gordon and I have been arguing that today's supercomputer centers will become superdata centers in the future," said Dr. Gray, an expert in large databases who has been working with some of the the nation's leading astronomers to build a powerful computer-based telescope.

The policy challenge spelled out by the Microsoft researchers comes as a quiet national policy debate over the future of supercomputing is taking place among experts in scientific, industrial and military computing.

In February the National Science Foundation Advisory Panel on Cyberinfrastructure issued a report calling on the nation to spend more than $1 billion annually to modernize its high-performance computing capabilities.

Separately, a study completed last year by a group of military agencies was released in April. Titled "Report on High Performance Computing for National Security," it calls for spending $180 million to $390 million annually for five years to modernize supercomputing for a variety of military applications.

Computer scientists added that the construction of the Japanese Earth Simulator, which is now ranked as the world's fastest supercomputer, has touched off alarm in some parts of the United States government, with some officials advocating even more resources for the nation's three national supercomputer centers, located in Pittsburgh, at the University of Illinois at Urbana-Champaign and at the University of California at San Diego.

Whatever decisions the government makes could have vast implications for computing.

The decision in 1985 to build a group of what were then five supercomputer centers linked together by a 56-kilobit-per-second computer network was a big impetus for development of the modern high-speed Internet, said Larry Smarr, an astrophysicist who is director of the California Institute for Telecommunications and Information Technology.

He said that Dr. Bell and Dr. Gray were correct about the data-centric technology trend and that increasingly the role of the nation's supercomputer centers would shift in the direction of being vast archives. Rapidly increasing network speeds would make it possible to increasingly distribute computing tasks.

Central to the Bell-Gray argument is the vast amount of data now being created by a new class of scientific instruments that integrate sensors and high-speed computers.

While the first generation of supercomputing involved simulating physical processes with relatively small data sets, the tremendous increase in data storage technology has led to a renaissance in experimental science, Dr. Gray said.

The nation should forget about financing the world's fastest computers, he said, and instead turn the nation's attention back toward science.

"The core of our argument is to give money back to the sciences and let them do the planning," he said.

Dr. Gray and Dr. Bell, a legendary computer designer who oversaw the national supercomputer centers for two years during the 1980's as a director for the National Science Foundation, call their current approach to computing "information centric" and "community centric." By rewriting existing scientific programs, they say, researchers will be able to get powerful computing from inexpensive clusters of personal computers that are running the free Linux software operating system. Many scientists are now adapting their work to these parallel computing systems, known as Beowulfs, which make it possible to cobble together tremendous computing power at low cost.

"The supercomputer vendors are adamant that I am wrong," Dr. Bell said. "But the Beowulf is a Volkswagen and these people are selling trucks."

The Bell-Gray proposal has been greeted with skepticism from the supercomputer centers and in some cases from scientists, too.

"I believe the dramatic increase in data the scientific community is producing will lead to the increasing importance of the scientific computing centers," said Horst D. Simon, a mathematician who is the director of the National Energy Research Scientific Computer Center in Berkeley, Calif.

He said that scientific research projects were turning increasingly to his computing center to take advantage of its professional management and technical support for managing their experiments' data.

Some other computer scientists say that Dr. Bell and Dr. Gray have correctly identified a fundamental technology trend, but that they are wrong in stating that the United States no longer needs to focus on developing the most powerful computers.

"Beowulf clusters are an attractive alternative," said Daniel A. Reed, director of the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign. "However, we still need a national-scale capability at the very high end."

A number of other scientists said they believed that Dr. Bell and Dr. Gray were overstating the power of the inexpensive Beowulf computing clusters.

"I'm not sure I agree with them on which is the cheap commodity computer and which is the specialized system," said Eric Bloch, a physicist at the Washington Advisory Group, a Washington-based science and consulting group, who is a former director of the National Science Foundation.

He said that supercomputer centers were still vital because they integrated systems that could be made available to scientific communities that might use the world's fastest computer if it were available.