NVIDIA Mellanox MCX556M-ECAT-S25 ConnectX-5 VPI Adapter, Dual-Port QSFP28 100Gb/s, Socket Direct, Tall Bracket: This is a ConnectX-5 VPI dual-port adapter card with Socket Direct architecture, providing two PCIe Gen3 x8 host connections joined by a 25cm internal harness. The card supports both EDR InfiniBand and 100GbE Ethernet on each QSFP28 port. NVIDIA P/N is 900-9X5AD-0056-DT1. This is a Socket Direct card, not a single-PCIe-edge card; it requires two PCIe Gen3 x8 slots on a dual-socket server. This is a new (NEW) unit.
Engineering Context
Socket Direct splits the card's PCIe interface into two independent x8 lanes, each routed to a different CPU socket via the 25cm harness. This avoids the QPI/UPI cross-socket hop for traffic served by the remote socket, reducing tail latency and improving NUMA locality. The card uses the ConnectX-5 ASIC with hardware offloads for RDMA over Converged Ethernet (RoCEv2) and InfiniBand verbs. VPI mode allows each port to be independently configured as InfiniBand or Ethernet at runtime via firmware. The 25cm harness length is the key differentiator from edge-only ConnectX-5 SKUs.
Deployment & Use Cases
HPC compute nodes running MPI workloads where PCIe locality matters. AI/ML training clusters with dual-socket servers feeding GPUs across NUMA boundaries. Storage servers using NVMe-oF over RDMA where both sockets serve I/O. Scientific simulation clusters using EDR InfiniBand. Mixed InfiniBand/Ethernet fabrics that may transition between protocols.
Technical Specifications
OEM: NVIDIA Mellanox
Part Number: MCX556M-ECAT-S25 (NVIDIA P/N: 900-9X5AD-0056-DT1)
Family: ConnectX-5 VPI
Port Configuration: Dual QSFP28
Data Rate: 100Gb/s per port (EDR InfiniBand or 100GbE Ethernet)
Host Interface: 2× PCIe Gen3 x8 (Socket Direct)
Harness Length: 25cm internal PCIe harness
Bracket: Tall (Full-Height)
Protocols: InfiniBand EDR, 100GbE, RoCEv2
Condition: New — Tested by T.E.S IT-SOLUTIONS
Compatibility & Constraints
Requires a dual-socket server with two available PCIe Gen3 x8 (or wider) slots, one routed to each CPU socket. The 25cm harness sets a fixed installation geometry; servers without compatible internal cable routing cannot accept this card. The card is full-height; it does not fit half-height/low-profile chassis without a different bracket. Compatible with NVIDIA Quantum (HDR backward to EDR) and Switch-IB 2 InfiniBand switches in EDR mode, and with NVIDIA Spectrum 100GbE switches. PCIe Gen4 hosts will negotiate down to Gen3.
Why TES
T.E.S IT-SOLUTIONS validates every ConnectX-5 VPI Socket Direct card for both PCIe lanes, link training on each port, and harness integrity before shipment. Refer to T.E.S IT-SOLUTIONS for compatibility advice on Socket Direct deployments. Handling time is 1–3 business days.