China's ambitions to become a major global power in the world of supercomputing were given a boost when one of its machines was ranked second-fastest in a survey.

The Nebulae machine at the National Supercomputing Centre in the southern city of Shenzhen can perform at 1.271 petaflops per second, according to the Top 500 survey (http://www.top500.org), which ranks supercomputers.

A petaflop is equivalent to 1,000 trillion calculations.

The United States still dominates the list, holding top spot with its Jaguar supercomputer at a government facility in Tennessee, and more than half of the systems on the list, released at a supercomputing conference in Germany.

But China has a total of 24 systems on the list, and two in the top ten, with the Tianhe-1 supercomputer in Tianjin ranking number seven.

And the Nebulae, built by Dawning Information Industry Co., Ltd., has a theoretical speed of 2.98 petaflops per second, which would make it the fastest in the world.

The machine's uses include scientific computing and gene sequencing, according to Chinese state media.

Calls to the company for further comment went unanswered.

The supercomputers on the Top 500 list are rated based on speed of performance in a benchmark test. Submissions are voluntary, so it does not include all machines.

The survey is produced twice-yearly.