The HP 4X DDR IB Mezzanine HCA is a single-port 4X DDR InfiniBand® PCI-Express Mezzanine adapter for HP c-Class server blades. The HP 4X DDR IB Mezzanine HCA can be plugged into PCI-Express connectors on HP c-Class server blades; however, to obtain the best performance, it is required to plug the HCA into the x8 PCI-Express connector on the server blades. The HP 4X DDR IB Switch Module is a double wide switch module for the c-Class enclosure. It has 16 downlinks to connect up to 16 server blades in the enclosure, and 8 uplinks to connect to the external InfiniBand switches to build an InfiniBand fabric. All links conform to InfiniBand Trade Association (IBTA) specifications. A subnet manager is required to establish an InfiniBand fabric. For HPC configurations, we support using Voltaire Grid Switch family products (internally managed switch) to provide the subnet management service. OpenSM from OpenFabric Enterprise Distribution can also be used to establish an InfiniBand fabric; however, support for OpenSM is only available from the OpenFabrics community.