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Institute of Astronomy


If the computing resources within the IoA are insufficient for the work you are undertaking, it is possible to obtain time on the University Research Computing Service high performance computing (HPC) x86 and GPU system ( which are collectively called Cambridge Service for Data Driven Discovery (CSD3). For further information, please visit Documentation on getting started, as well as the User Guide is available at

A useful starting point is at:

Computing time can be obtained via peer reviewed UK national allocation programmes like DIRAC or IRIS. Information about purchasing time is here:

There is also 'free' time at lower queue priority called Service Level 3 (SL3). The Service Levels are described at the link below:

The email address for the HPC helpdesk is: Note the IoA IT helpdesk does not support the HPC system.

Service Level 3 (SL3)  – Free Usage

[correct on 18th Oct, 2022] Service Level 3 (SL3) operates with the medium quality of service, QOS2. QOS2 is lower than QOS1 which is used in SL1 & SL2. This service level is designed for groups with medium usage requirements who currently do not have funding to pay for their usage, thus an immediate conversion of funds into credits is not required.

SL3 is capped with a maximum number of usage credits per PI per quarter. This has been introduced to promote a more even usage of the free time on the system. Currently each PI may receive 200,000 X86 CPU core hours and 3000 GPU hours per quarter. (There are 8760 hours in a year, so the free allocation is equivalent to 100 X86 CPU cores and  1.5 Nvidia A100 SXM4 80GB  GPUs running continuously at 100% for 1 year).

There is no guaranteed minimum usage level for SL3 and there is no concept of expiry or of moving core hours across quarters. Once a group in SL3 has consumed all its allowed core hours in a quarter, jobs can still be submitted at Service Level 4.

Purchasing Computing Time or Storage

IoA Local contacts

Debora Sijacki (, Martin Bourne (, Richard McMahon (

Some useful resource accounting commands on CSD3


see for more information.