Nothing to do with Virtual Iron, but the key is that becasue it isn't a standard NUMA architecture such as SGI Altix thelatency question is not relevant. The COMA memory chunk, caches Gigabytes of data. Predictive algorithms prefetch data blocks so that when computation is needed they are already resident in memory, hence no IB latency issue. The net issue is MPIcodesat the same speed as an IB cluster, support for large shared memory jobs, without cluster management complexity.
As far as the IB is converned the system uses standard Mellanox IB, including ConnectX if it shipping yet.
The larger, 8-32 socket system uses an internal IB switch to connect servers together.