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 Status


Since 10 Jul. 2024


Work performed on the Janet network link was completed. Please report any further network issues via the servicedesk.


Since 10 Jul. 2024


The MACS system is currently experiencing issues with job submissions. We are in conversation with our vendor to help resolve this.


The Isambard 2 service will shutdown in 2024 (service extended from previous June date to now be after the summer) and be replaced with an entirely new Isambard 3 service. Data management is the responsibility of the user therefore we require all important data moved off Isambard 2 before it is shutdown. Support will only be provided for operational issues until the shutdown. Further information will be provided over the coming months.

On Tuesday June 4th 2024 at 9am the “PHASE 3” was switched OFF and was moved to Bristol to be part of Isambard 3 which will be launched over the summer.

System Status


10 Jul. 2024

  • Login bastion: Available.

  • XCI (ARM ThunderX2): Available.

  • MACS: Job submission issues.

  • A64fx: Available.

  • Phase 3: Switched off - see announcement above.

Mailing list

An anouncement mailing list is availale to be kept informed of important news regarding the service. Archives and managing your subscription is available at JiscMail GW4-ISAMBARD-COMMUNITY

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)

Indices and tables