The US Department of Energy possesses the fastest, most powerful computer in the world, a semiannual ranking of computing systems around the world said. The new titleholder is the Titan computer at the department\'s Oak Ridge National Laboratory in Tennessee, the Top500 listing announced at the SC12 International Conference for High Performance Computing, Networking, Storage and Analysis in Salt Lake City. Titan replaced the laboratory\'s Jaguar computer last month, which had ranked as the world\'s fastest computer on the Top500 lists in November 2009 and June 2010. \"The new Top500 list clearly demonstrates the U.S. commitment to applying high-performance computing to breakthrough science, and that\'s our focus at Oak Ridge,\" ORNL Director Thom Mason said. \"We\'ll deliver science from Day One with Titan, and I look forward to the advancements the Titan team will make in areas such as materials research, nuclear energy, combustion and climate science.\" Titan is a Cray XK7 system of 18,688 nodes, each with a 16-core AMD Opteron 6274 processor and an NVIDIA Tesla K20X graphics processing accelerator, and the computer has 710 terabytes of memory, an ORNL release said Monday. Titan reached a speed of 17.59 petaflops -- quadrillion calculations per second -- in a benchmark test used to rank supercomputers on the Top500 list. Titan is capable of a theoretical peak speed of 27 petaflops while using approximately 9 megawatts of electricity, roughly the amount required for 9,000 homes.