Nodes in a P7-IH [20] cluster are connected in a two-level dragonfly network topology. The core of the network is the Hub Chip, which
connects several high-bandwidth links using a high-performance internal crossbar switch. These links, providing over 9 Tbits/second
of raw bandwidth, are used to build a two-level topology spanning
up to tens of thousands of POWER7 processor chips, offering high
bisection bandwidth and low latency.
BG/Q uses a 5-dimensional (5D) torus. Each compute node is
equipped with 11 communication links, each of them supporting
4GB/s of bi-directional bandwidth. Ten of the links are used to create the 5D torus, while the eleventh connects the compute node to
an I/O node