For the first time since November 2009, a US supercomputer sits atop the Top500 list of the world’s top supercomputers. Sequoia, the IBM BlueGene/Q system installed at the Department of Energy’s Lawrence Livermore National Laboratory, achieved an impressive 16,32 petaflops per second on the Linpack benchmark using 1 572 864 cores.

Sequoia is also one of the most energy efficient systems on the list, announced today at the 2012 International Supercomputing Conference in Hamburg. This is the 39th edition of the list, which is compiled twice each year.

On the latest list, Fujitsu’s “K Computer” installed at the RIKEN Advanced Institute for Computational Science (AICS) in Kobe, Japan, is now the number two system with 10,51 petaflops per second on the Linpack benchmark using 705 024 SPARC64 processing cores. The K Computer held the top spot on the previous two lists.

The new Mira supercomputer, an IBM BlueGene/Q system at Argonne National Laboratory in Illinois, debuted at number three, with 8,15 petaflops per second on the Linpack benchmark using 786,432 cores. The other US system in the Top 10 is the upgraded Jaguar at Oak Ridge National Laboratory in Tennessee, which was the top US system on the previous list and now clocks in at number six.

The newest list also marks a return of European systems in force. The most powerful system in Europe and No.4 on the List is SuperMUC, an IBM iDataplex system installed at Leibniz Rechenzentrum in Germany. Another German machine, the JuQUEEN BlueGene/Q at Forschungszentrum Juelich, is number eight.

Italy makes its debut in the Top 10 with an IBM BlueGene/Q system installed at CINECA. The system is at number seven on the list with 1,72 petaflops per second performance. In all, four of the top 10 supercomputers are IBM BlueGene/Q systems. France occupies the number nine spot with a homegrown Bull supercomputer.

China, which briefly took the number one and number three spots in November 2010, has two systems in the Top 10, with Tianhe-1Aat the National Supercomputing Center in Tianjin in number five, and Nebulae at the National Supercomputing Centre in Shenzhen number 10.

Total performance of all the systems on the list has increased considerably since November 2011, reaching 123,4 petaflops per second. The combined performance of the last list was 74,2 petaflops per second. In all, 20 of the supercomputers on the newest list reached performance levels of 1 petaflop per second or more. The number 500 machine on the list notched a performance level of 60,8 teraflops per scond, which was enough to reach number 332 just seven months ago.

A total of 372 systems (74,4%) are now using Intel processors, down from 384 systems (76,8%) on the last list. Intel is now followed by the AMD Opteron family with 63 systems (12,6%), same as in the in the previous list. The share of IBM Power processors has increased from 49 to 58 systems (11,6%).

A total of 58 systems use accelerators or co-processors (up from 39 six months ago), 53 of these use NVIDIA chips, two use Cell processors, two use ATI Radeon and there is one new system with Intel MIC technology.

IBM kept its lead in systems and has now 213 systems (42,6%) compared to HP with 138 systems (27,6%). HP is slightly down from 141 systems (28,2%) seven months ago, compared to IBM with 223 systems (44,6%). In the system category, Cray, Appro, SGI and Bull follow with 5,4%, 3,6%, 3,2%, and 3,2% respectively.