5: Tianhe-1A (China)

China's electronic pride and joy, Tianhe-1A, was the fastest supercomputer in the world in 2010. It slipped to second place in 2011 and now sits in the number five spot. Like the Nebulae, Tianhe-1A's performance is bolstered by graphics card maker Nvidia. It uses 168 Nvidia Tesla M2050 GPUs to offload work from its 14,336 Intel Xeon processors. In total, it runs on more than 180,000 computer cores [source: CNET].
Unlike Nebulae, Tianhe-1A is not made by Chinese computer company Dawning. Instead, it comes from China's National University of Defense Technology. It operates at the National Supercomputing Center at Tianjin. Tianhe-1A can crank out 2.5 petaflops of performance, making it twice as fast as China's next-best supercomputer.

4: SuperMUC

Despite being another IBM system using Intel's Xeon processors, the SuperMUC is unique in a couple different ways. Located in Germany's Leibniz Supercomputing Centre, the SuperMUC uses a new hot-water cooling system to keep the computer's brain from frying while it's performing billions upon billions of operations. The SuperMUC is another new entry on the list and performs at up to 3 petaflops, thanks to about 150,000 processing cores.
Efficiency is what really sets the SuperMUC apart: IBM says it's 40 percent more energy efficient than an air-cooled system would be. They claim the water removes heats 4,000 times more efficiently than air. Thanks to its cutting-edge hardware, the SuperMUC is Germany's fastest supercomputer. In fact, it's the fastest supercomputer in Europe, period.

3: Mira (United States)

Here's where supercomputers get serious. The first seven entries on the list were fast, but not fast enough for top-three ranking. IBM's new Mira, which becomes fully operational in 2013, peaks at a performance of 8 petaflops. That's more than twice as fast at the SuperMUC in Germany.
Mira runs on 768,000 processor cores. It's located at the Argonne National Laboratory, a research laboratory run for the United States Department of Energy. It uses IBM's BlueGene/Q platform and replaces an older IBM system, Intrepid, which ranked fourth on the list in 2008.
Researchers who submit proposals for the Innovative and Novel Computational Impact on Theory and Experiment program will be able to claim processor time on Mira. Sixty percent of the computer's capacity will go to their research, while 30 percent will go towards the Advanced Science Computing Research Leadership Computing Challenge. The final 10 percent will be reserved for urgent, time-sensitive computations [source: Information Week].

2: K computer (Japan)

Fujitsu's K computer, the only supercomputer in Japan that made the top 10, is an incredibly powerful machine. It reigned as the fastest supercomputer in the world on both 2011 lists and now sits at No. 2 with a huge gulf in performance over IBM's new Mira. It can perform at up to 11 petaflops.
The K Computer is located at Japan's RIKEN Advanced Institute for Computational Science, where it performs scientific operations including global disaster prevention, meteorology and medical research [source: Fujitsu]. Unlike many of the other supercomputers on the list, it doesn't run on IBM architecture. The K computer uses Fujitsu's own SPARC64 VIIIfx octo-core processors. Seven hundred and five thousand computer cores help it churn through operations at an incredible pace.
But believe it or not, the fastest supercomputer in the world is leaps and bounds more powerful than the K computer.

1: IBM Sequoia (United States)


 
This is the Big Kahuna, the champion on the June 2012 TOP500 list. IBM's Sequoia is the fastest computer in the world (at least, the fastest visible to the public) thanks to 1.6 million processing cores that can crank out an incredible 16.3 petaflops of performance. Wondering just how incredible that is?
Well, if we look back a mere half decade, to 2008, IBM's Roadrunner made history (and grabbed the top slot) for cracking 1 petaflop, aka performing 1,000 trillion operations per second [source: IBM]. IBM said Roadrunner was equivalent to 100,000 of 2008's laptops in performance. And Sequoia is 16 times as fast! Sequoia is one of four computers on the June 2012 list running on the BlueGene/Q IBM design, an 18 core 1.6GHz chip. That's not an especially fast clock speed by today's standards, but with 96 racks of chips, the performance really adds up.
What's Sequoia doing with all that speed, anyway? For a while, IBM has bragging rights -- Sequoia is 55 percent faster than the second fastest computer on the list. But they're putting Sequoia to work, of course. The computer operates at the U.S. Department of Energy's National Nuclear Security Administration at the Livermore National Laboratory. The computer's doing important work: One of its responsibilities is simulatingnuclear explosions.