NVIDIA Mellanox ConnectX-5 MCX556M-ECAT-S25
ConnectX-5 VPI Socket Direct adapter, dual-port EDR IB (100Gb/s) / 100GbE, 2x PCIe 3.0 x8
Host Interface
Socket Direct — 2x PCIe 3.0 x8 (dual-socket auxiliary connection)
Port Count
2-port
Port Speed & Connector Type
100Gb/s QSFP28 — EDR InfiniBand (100Gb/s) or 100GbE, per port
Network Protocol
VPI — InfiniBand and Ethernet (selectable)
RDMA
Native InfiniBand transport; RoCE v2 (Ethernet mode)
Product Description
The NVIDIA Mellanox ConnectX-5 MCX556M-ECAT-S25 is a dual-port VPI adapter built on NVIDIA's Socket Direct architecture, splitting its PCIe interface into two physical x8 edges (2x PCIe 3.0 x8) connected via an auxiliary riser/harness, rather than a single x16 connector. This allows the card to connect directly to two CPU sockets in a dual-socket server, giving each socket a direct, low-latency path to the network without traversing the inter-CPU interconnect (QPI/UPI) — a significant advantage for GPUDirect RDMA, NVMe-oF, and NUMA-sensitive HPC workloads. Built on the MT28808A0-FCCF-EVM controller, it supports 100Gb/s EDR InfiniBand or 100GbE on each of its two QSFP28 ports, with native InfiniBand transport offload and RoCE v2 in Ethernet mode. The S25 designation identifies this SKU's specific auxiliary card/riser configuration; it is intended for multi-socket HPC and AI servers where balanced, socket-local PCIe bandwidth matters as much as raw port speed.