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Modes of operation

When running jobs on the system users can choose whether they wish to run in single node (SN) mode or virtual node (VN) mode. In SN mode only one of the dual core processors will be utilised leaving the second core idle. In this case all 6 GB of memory will be available to the single core. In VN mode both of the cores are used and the memory gets shared between them, making 3 GB available to each core. At present the 6 GB memory is composed of one 2 GB and one 4 GB dimm which means round-robining or stripping of memory is not possible. For codes which are memory bound their performance may be adversely affected as a result. In future it is hoped that the system will be re-configured to provide a symmetric memory distribution, e.g. two 2 GB or two 4 GB dimms.