What just happened? The bi-annual TOP500 Supercomputer list usually sees China and the US battling for the top spot, but not anymore. In the latest, 55th edition of the rankings, Japan has taken the number one position for the first time since 2011. It's also the first instance of an ARM-based computer beating all others.

Japan's system, Fugaku, which is installed in Kobe and developed by Fujitsu and the government-sponsored Riken institute, managed a High Performance Linpack (HPL) result of 415.5 petaflops. That makes it around 2.8 times faster than the now second-place Summit from IBM. The system also came first in the High-Performance Conjugate Gradient (HPCG) Benchmark with a record 13.4 HPCG-petaflops.

It took six years to develop Fugaku, which uses Fujitsu's 48-core A64FX system-on-chip. It's the first time an ARM-based processor has grabbed the top position---there are only four of these systems in the TOP500, three of which use the same Fujitsu processor. The x86 architecture is used in 481 systems, and 469 of these are from Intel.

Thanks to the addition of Fugaku, the aggregate list performance has jumped from 1.65 exaflops six months ago to 2.23 exaflops. The latest edition sees the lowest number of new systems (51) since the TOP500 began in 1993, possibly a result of Covid-19-related delays.

Back in 2017, China overtook the US when it came to the number of supercomputers on the list. Back then, it had 202 entries, compared to America's 143. Now, China has 226, while the US has fallen to 114. Japan is third with 30, followed by France (18), and Germany (16).

Despite being second to China in terms of overall supercomputer numbers, the US is still number one in aggregate list performance, boasting 644 petaflops to its rival's 565 petaflops.

Fugaku has been used for Covid-19 research, and it's hoped the $1.2 billion machine will help identify treatments for the virus when it goes into full operation next year. It will also be used to model the impact of earthquakes and tsunamis and map out escape routes.