The Cray XD1 is a
specialized system with 6 dual opteron compute blades, with FPGA-based custom
interconnect adapters by Cray, connected by a Mellanox Infiniband switch chip.
The FPGA's are directly connected to the opteron processors via Hypertransport,
so this is the currently the only InfiniBand-based system that does not use
a mellanox adapter chip we have.
Peak Bandwidth on XD1 vs InfiniBand and Dolphin SCI (SISCI)