The High Performance Computing processor market has been dominated by Central Processor Unit (CPU) vendors such as Intel and AMD for the last twenty years. During this period, the rates of improvement in processor performance have been slowing to the extent that recent supercomputers have struggled to deliver the performance required to tackle important scientific challenges such as modelling climate change or simulating how viruses work in the human body.

Opening up the market

To address this problem a team of researchers at the Faculty of Engineering formed Isambard – a project focused on building the world’s first production supercomputer based on a CPU architecture originally designed by British semiconductor company Arm, for mobile devices like smartphones.

Arm’s goal has been to create a licensable architecture that would enable multiple chip companies to license the core technology before customising it, resulting in a vibrant market where multiple processor vendors could compete over performance, price and other features while providing solutions compatible with one another.

Breakthrough research

Backed by £3m in EPSRC funding, the team at Bristol, along with collaborators in the GW4 Alliance and the Met Office, designed Isambard to enable scientifically rigorous and reproducible results by integrating new, state-of-the-art Arm-based processors from Marvell (a US-based semiconductor company) alongside best-in-class processors from Intel, AMD and NVIDIA.

Isambard also included leading software suites and established code optimisation best practice, enabling the first ever best-to-best comparisons between all the main competing computer architectures.

Isambard’s results were the first to prove that open, Arm-based production supercomputers could be performance-competitive with the current state-of-the-art supercomputers, both at the single server level and at the system level, while potentially delivering up to three times the performance per dollar at the processor level.

The research also included rigorous benchmarking, comparing performance across a range of scientific software applications from computational chemistry, biochemistry, materials modelling, engineering and climate modelling.

Wide adoption and commercial success

Isambard’s impact has led to a new breed of supercomputers, opening up a new multi-million Pound market for Arm and directly leading to Arm-based systems being deployed across the US, Europe, Japan and China.

Isambard has been in use at the UK Met Office to help it process the Unified Model, the numerical model of the atmosphere it uses for both weather prediction and climate change modelling applications.

The project has given birth to a whole generation of Arm-based supercomputers. These include Fugaka, the fastest supercomputer in the world developed at the RIKEN scientific research institute in Japan. Fugaka can perform more than 415 quadrillion computations a second and has been used during the COVID-19 pandemic in searches for Coronavirus treatment.

Other scientific applications that have been ported to Isambard-based systems include VASP, the electronic structure chemistry code from the University of Vienna, one of the most widely used codes on supercomputers around the world, and OpenFOAM, a widely used open-source computational fluid dynamics code.

Isambard resulted in significant benefit to its industrial partners, including Marvell, the US-based semiconductor company which developed the Arm-based CPUs used in the project. Marvell went on to win a number of other projects related to the production of Arm-based supercomputers around the world.

Isambard was so beneficial for both Arm and Marvell that both organisations contributed substantial investment into a follow-on project, Isambard 2, which has since delivered new advancements in supercomputer performance that have further accelerated scientific research, continuing to make valuable contributions in the years and decades to come.