Fugaku and A64FX: the First Exascale Supercomputer and its Innovative Arm CPU

Abstract

Fugaku is the first exascale supercomputer in the world, designed and built primarily by Riken Center for Computational Science (R-CCS) and Fujitsu Ltd., but involving essentially all the major stakeholders in the Japanese HPC community. The name ‘Fugaku’ is an alternative name for Mt. Fuji, and was chosen to signify that the machine not only seeks very high performance, but also a broad base of users and applicability at the same time. The heart of Fugaku is the new Fujitsu A64FX Arm processor, which is 100% compliant to Aarch64 specifications, yet embodies technologies realized for the first time in a major server general-purpose CPU, such as 7nm process technology, on-package integrated HBM2 and terabyte-class SVE streaming capabilities, on-die embedded TOFU-D high-performance network including the network switch, and adoption of so-called ‘disaggregated architecture’ that allows separation and arbitrary combination of CPU core, memory, and network functions. Fugaku uses 158,974 A64FX CPUs in a single socket node configuration, making it the largest and fastest supercomputer ever created, signified by its groundbreaking achievements in major HPC benchmarks, as well as producing societal results in COVID-19 applications.