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Slow Processors Power Super-Speedy Computer

In a California laboratory, there's a cold, white room that looks like a scene right out of 2001: A Space Odyssey. Inside, there's a loud hum and eight rectangular cabinets that look like black, shiny, inscrutable monoliths. They hold a supercomputer called BlueGene. This week, it was named the fastest computer in the world. But surprisingly, it's built from the same kind of slow processors that would run your cell phone.

BlueGene can do more than 280 trillion calculations a second. That's like every single person on Earth -- man, woman and child -- each doing 40,000 math problems in the blink of an eye. The computer is housed at Lawrence Livermore National Laboratory, in Livermore, Calif., where it was built to do simulations of nuclear tests. The computer "is probably on the order of a hundred thousand times more powerful than a powerful desktop system," says Dave Turek, who works on supercomputing at IBM, which built the chips inside BlueGene.

And BlueGene is faster than anything else on the planet. That's according to an organization called TOP500, which ranks supercomputers. It released its latest rankings at a conference in Seattle this week.

Now, you might think that a champion supercomputer would use the fastest, hottest chips around. But Turek says you'd be wrong: "What we did with BlueGene was something absolutely counterintuitive at the time we began the project."

Most supercomputers are made by stringing together a bunch of off-the-shelf processors, the kind that power a high-end desktop. The problem is that these fast processors use a lot of power, generate a lot of heat, and are hard to string together in an efficient way. So Turek says BlueGene relies on processors that are relatively weak: "Because they're smaller and because they run slower, they also are cooler, and you can put more of them in a certain amount of physical space."

BlueGene packs 131,000 processors into a space the size of a tennis court. That's way more than your typical supercomputer, which has just a few hundred or a few thousand.

Turek says BlueGene's processors, plus a couple of other tricks, helped it unseat Japan's Earth Simulator, the previous world champion. Earth Simulator is the size of a football stadium and designed to model things like earthquakes and weather. It can run a mere 35 trillion calculations per second. Back in 2002, when Earth Simulator was turned on, it was five times faster than its nearest competitor. "It was something that appeared suddenly on the scene and far outstripped the most powerful computer in play at that time," says Turek.

Earth Simulator reigned as speed king for three years -- longer than any other computer. That worried many American scientists, who saw it as a poor reflection on the state of the American computing industry. So they were overjoyed when BlueGene beat Earth Simulator for the first time last year -- it was twice as fast.

Now, by adding more processors, the BlueGene team has made their computer 10 times faster than Earth Simulator. And nothing else on the TOP500 list comes close. "I’m very impressed. I'm impressed that they can get a machine of that size together, and they can have it operate for a long period of time, and it's being used today to do very challenging computations," says Jack Dongarra of the Innovative Computing Laboratory at the University of Tennessee in Knoxville.

BlueGene is a government machine that scientists will use to study classified things like atomic bomb blasts. So not too many scientists will get a chance to use it. But experts say that the technology used in elite machines like BlueGene will eventually trickle down to more run-of-the-mill supercomputers used by thousands of scientists. Those machines help do everything from designing diapers to managing the stock market.

How long will BlueGene stay on top of the list? No one knows. The once-invincible Earth Simulator is now down at number seven, and Dongarra says faster supercomputers are on the drawing boards.

Copyright 2022 NPR. To see more, visit https://www.npr.org.

Nell Greenfieldboyce is a NPR science correspondent.