For example, the hope is that Vista Azul could do large calculations on one set of nodes, render the data on another cluster, then turn that data over to the graphics engine. The group is still working out bugs in the new system. This type of system would also be advantageous for those who have old IBM SPs, Pineda said. Rather than take an old SP and throw it away, you could graft new Linux clusters on to the existing platform. Because the processors of Linux-based clusters are not wired together internally for ultrafast communication like standalone supercomputers, a critical component is the communications network that connects the nodes.
Communication has to happen fast.
For low-end clusters, a network known as FastEthernet usually does the job. But if a cluster is to take its place alongside enormous standard supercomputers, it needs something more sophisticated, such as Gigabit Ethernet or Myrinet. Gordon's colleague David Halstead put SCI to the test. His particular concern was that SCI's communication through nodes is monodirectional. For example, to get from node 1 to node 8 requires going through several other nodes.