Twice a year, the Top500 list outlines the world's most powerful supercomputers, and the US has always held the title of most units in that list – that is, until it was knocked off its perch by China back in June. With the latest rankings released this week, the former champion is clawing its way back to the top, with the US and China now tied for 171 systems each within the top 500.

This time last year, the US held the lead easily, with 200 of the 500 most powerful supercomputers, almost double that of China. By June 2016, that figure dropped to 165 while China's jumped to 167, including the top two positions on the list – both of which remain unchanged in the latest rankings.

With over 93 petaflops of processing power, the Sunway TaihuLight is far and away the most powerful supercomputer in the world, absolutely smashing its nearest competitor, the Tianhe-2, which is humming away on a still-not-to-be-scoffed-at 34 petaflops. But two new entries have shaken up the top 10: the Cori supercomputer at Berkeley Lab's National Energy research Scientific Computing Center, debuted at number five with 14 petaflops, and right behind it was the Oakforest-PACS in Japan, at 13.6 petaflops.

Interestingly, the most energy-efficient machine fell well outside the top 10. Coming in at number 28 on the list, Nvidia's DGX SATURNV may only have 3.3 petaflops of power, but it performs at an impressive 9.46 gigaflops per watt.

In testament to the never-ending march of technology, the top 117 systems on the ladder are now operating at speeds greater than a petaflop, compared to 81 machines last November. The petaflops barrier was first broken in 2008, and now the next target on the horizon is a supercomputer on the scale of exaflops (1,000 petaflops), which the White House hopes to develop by 2025.

Source: Top500