K computer (Japan)
Fujitsu's K computer, the only supercomputer in Japan that made the top 10, reigned as the fastest supercomputer in the world on both 2011 lists, but has since been edged down to No. 4. Still, it breaks the single-digit barrier and makes a noticeable jump in speed over IBM's Mira with a performance of 10.5 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. Its 705,000 computer cores help it churn through operations at an incredible pace.
But believe it or not, the last three fastest supercomputers are leaps and bounds more powerful than the K computer.