Isambard User Documentation

Isambard is a HPC service provided by GW4 and the UK Met Office. The system is funded by EPSRC and is one of a number of Tier-2 HPC facilities in the UK.

Isambard is a Cray XC50 system which comprises 20,992 cores, and is one of the world’s first production Arm-based supercomputers. While Isambard is not based on the more common x86 processors from Intel and AMD, most software compiles and runs on Isambard with no or minimal changes.

Each of the 329 compute nodes contain two 32-core Marvell ThunderX2 processors running at 2.5 GHz. 160 nodes have 256 GB and 169 have 512 GB of memory, both at DDR4-2666MHz. The nodes are connected via Cray Aries interconnect in a Dragonfly topology. A Cray Sonexion 3000 storage cabinet provides 900 terabytes of Lustre storage.

Service Interruption


15 Sep. 2021

Authentication issues have resulted in jobs failing and login issues early this morning, the cause has been identified and the issue fixed, with improvements to avoid it reoccuring.

Users are recommended to check their jobs: Any running jobs likely failed due to Permission Denied filesystem errors; Queued jobs likely attempted to run and failed immediately.

Apologies for any inconvenience, please contact if you experience any further issues.

System Status


2 Jun. 2021

  • XCI (ARM ThunderX2): Available

  • MACS: Available

  • A64fx: Available

Acknowledging Isambard

Research outputs that have made use of Isambard should acknowledge the facility by using the following phrase:

This work used the Isambard 2 UK National Tier-2 HPC Service ( operated by GW4 and the UK Met Office, and funded by EPSRC (EP/T022078/1)

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