I quote from a recent article in The Economist:
“Titan” (the newly proclaimed world's fastest supercomputer) lives at Oak Ridge National Laboratory, in Tennessee. It took first place from another American machine, IBM’s “Sequoia”, which is housed at Lawrence Livermore National Laboratory, in California. These two machines have helped reassert America’s dominance of a list that had, in the past few years, been headed by computers from China and Japan.The Digital Divide is alive and well, and living in the upper reaches of super computing!
Titan is different from the previous champion in several ways. For one thing, it is an open system, meaning that scientific researchers with sufficiently thorny problems will be able to bid for time on it, in much the same way that astronomers can bid for time on telescopes. Sequoia, by contrast, spends most of its time running hush-hush simulations of exploding nuclear weapons, and is therefore rarely available for public use.
Titan has an unusual design, too. All supercomputers are composed of thousands of processor chips harnessed together. Often, these are derivatives of the central processing units, or CPUs, that sit at the heart of modern, desktop machines. But Titan derives the majority of its oomph—more than 90%—from technology originally developed for the video-game industry. Half of its 37,376 processors are ordinary CPUs. But the other half are graphics processing units, or GPUs. These are specialised devices designed to cope with modern video games, which are some of the most demanding applications any home machine is ever likely to run.