IBM's Mira, which became fully operational in 2013, peaks at a performance of 8.6 petaflops. That's more than 2 petaflops over the Piz Daint, and nearly 3.5 petaflops more than Stampede.
Mira runs on 786,000 processor cores. It's located at the Argonne National Laboratory, a research laboratory for the U.S. 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 (INCITE) through the U.S. Department of Energy's Office of Science can claim processor time on Mira. Sixty percent of the computer's capacity goes to their research, while 30 percent goes towards the Advanced Science Computing Research Leadership Computing Challenge. The final 10 percent is reserved for urgent, time-sensitive computations [source: Information Week].