The world's fastest machine with no accelerator
On 9 March 2021 RIKEN announced that development of Fugaku was complete and the machine was open for shared use. Its 158,976 nodes each hold one Fujitsu A64FX processor on the Arm architecture, with 48 compute cores plus two assistant cores and 32 gibibytes of HBM2 at 1024 gigabytes per second, and no separate accelerator at all. Linpack measured 442.01 petaflops.
Why it matters
The fastest machine in the world at that moment was built unlike any that followed it: no graphics accelerators, no x86, and a processor designed in the country it stands in. That shows computing independence was still reachable in 2021, and shows what it costs, since nobody has attempted the same route since.
RIKEN and Fujitsu developed it from 2014 as the core of Japan's High Performance Computing Infrastructure under the Ministry of Education, Culture, Sports, Science and Technology. Nodes are packed two to a board, sixteen to a blade bunch, forty-eight to a shelf and 384 or 192 to a rack; there are 432 racks, making 158,976 nodes. Between nodes runs a six-dimensional mesh and torus interconnect. From June 2020 to November 2021 the machine stood first in four rankings at once across four consecutive lists. What the record does not claim. The report's figure of more than 2 exaflops in mixed precision on HPL-AI is not confirmed here: the relevant TOP500 list pages return 404 and no primary source for the number was found, so it does not enter. Nor does the project cost estimate, nor the share of machine time given to open science: neither figure appears on any page that was checked.