I.B.M. said the machine was up to 42 percent faster than its fastest 80286-based machines.

In fact, American companies now manufacture 16 of the 20 fastest machines.

Seven of the 10 fastest machines are now in the United States.

But the fastest American machines are used primarily for military applications at the nation's weapons laboratories.

Nevertheless the machine was air cooled, and would have been the fastest such machine on the market.

Mr. Cray had insisted that the company focus on building only the very fastest machines.

For software developers and rocket scientists who demand the fastest machines on the market, the power reduction from a 25-megahertz 386 chip might be unacceptable.

But the fastest machines are so expensive they must be shared.

The fastest machine uses a 25-megahertz 80386 chip, company officials said.

It is at least 10 times more powerful than the fastest rival machine.