WASHINGTON - China's Tianhe-2, a supercomputer capable of operating as fast as 33.86 petaflops per second (Pflop/s), remains the world's most powerful system, according to a biannual Top500 list of supercomputers released Monday.

Tianhe-2, developed by China's National University of Defense Technology, put China back at the top of the list in June. It is almost twice as fast as the next computer on the list, Titan of the US Department of Energy (DOE), which has a performance of 17.59 Pflop/s.

"The Tianhe-2 is a very powerful computing system," Jack Dongarra, professor of the University of Tennessee and Top500 editor, told Xinhua. "It has almost two times the performance of the number 2 system, Titan. I wouldn't be surprised if it was in the number 1 position for another year."

Except for its computing chips, Tianhe-2 uses technologies that have almost all been developed and built in China, including the interconnect system, operating system, front-end processors and software.

"The major challenge is for China to develop the computing chip technology so it can build the whole computer with Chinese parts. Application software also presents a great challenge," Dongarra said.

In November 2010, Tianhe-2's predecessor, Tianhe-1A, took the first spot but was overtaken by Japan's K computer six months later. Tianhe-1A is now No. 12 on the list.

Sequoia, installed at the DOE's Lawrence Livermore National Laboratory, is again the No. 3 system with a performance of 17.17 Pflop/s. Japan's K computer is the No. 4 system with 10.51 Pflop/s, followed by Mira, installed at the DOE's Argonne National Laboratory, which has a performance of 8.59 Pflop/s.

The new entry in the Top10, Piz Daint, is at No. 6. The machine installed at the Swiss National Supercomputing Center achieved 6.27 Pflop/s. It is now the most powerful system in Europe and also the most energy efficient system in the Top10.

The total combined performance of all 500 systems on the list is 250 Pflop/s, according to the list. Half of the total performance is achieved by the top 17 systems on the list, with the other half of the total performance spread among the remaining 483 systems.

Overall, the United States is "clearly the leading consumer" of the supercomputing systems with 265 entries on the list. As a nation, China holds the No. 2 position with 63 entries, behind the United States but ahead of Japan, Britain, France and Germany, the list showed.

The Top500 list, released twice a year since June 1993, is considered the authoritative ranking of the world's supercomputers. It is compiled on the basis of the machines' performance on the so-called Linpack benchmark by Dongarra and other experts from the United States and Germany.