For three years running, the fastest supercomputer has been NEC's Earth Simulator in Japan.
"The fact that non-U.S. vendor like NEC had the fastest computer was seen as a big challenge for U.S. computer industry," said Horst Simon, director of the supercomputing center at Lawrence Berkeley National Lab in California.
"That an American vendor and an American application has won back the No. 1 spot — that's the main significance of this."
Earth Simulator can sustain speeds of 35.86 teraflops.
IBM said its still-unfinished BlueGene/L System, named for its ability to model the folding of human proteins, can sustain speeds of 36 teraflops. A teraflop is 1 trillion calculations per second.
Lawrence Livermore National Laboratory plans to install the Blue Gene/L system next year with 130,000 processors and 64 racks, half a tennis court in size. The labs will use it for modeling the behavior and aging of high explosives, astrophysics, cosmology and basic science, lab spokesman Bob Hirschfeld said.
The prototype for which IBM claimed the speed record is located in Rochester, Minn., has 16,250 processors and takes up eight racks of space.
While IBM's speed sets a new benchmark, the official list of the world's fastest supercomputers will not be released until November. A handful of scientists who audit the computers' reported speeds publish them on Top500.org.
Supercomputing is significant because of its implications for national security as well as such fields as global climate modeling, astrophysics and genetic research.
Supercomputing technology IBM introduced a decade ago has evolved into a $3 billion to $4 billion business for the company, said Simon.
Unlike the more specialized architecture of the Japanese supercomputer, IBM's BlueGene/L uses a derivative of commercially available off-the-shelf processors. It also uses an unusually large number of them.
The resulting computer is smaller and cooler than other supercomputers, reducing its running costs, said Hirschfeld. He did not have a dollar figure for how much lower Blue Gene's costs will be than other supercomputers.
However, other supercomputers can do things Blue Gene cannot, such as produce 3-D simulations of nuclear explosions, Hirschfeld said.