NVIDIA Mellanox MCP1660-W003E26 — LinkX 400GbE QSFP-DD Passive Copper DAC, 3 m, 26 AWG

Technical Identity
The NVIDIA Mellanox MCP1660-W003E26 is a LinkX 400GbE passive copper Direct Attach Cable (DAC) with QSFP-DD connectors on both ends, fixed at 3 m reach and built on 26 AWG twin-axial pairs for the longer end of the 400G passive copper loss budget. It is a single 400GbE link (1× QSFP-DD → 1× QSFP-DD) — not a 2×200G or 8×50G breakout. Engineered for intra-rack and short adjacent-rack switch-to-adapter or switch-to-switch wiring in 400GbE Spectrum Ethernet fabrics. Supplied by T.E.S IT-SOLUTIONS in Refurbished Grade A condition, bench-tested for link integrity at native 400GbE before dispatch.

Specifications

Brand: NVIDIA (Mellanox LinkX)
Model / MPN: MCP1660-W003E26
Product type: Passive Copper Direct Attach Cable (DAC)
Family: LinkX 400GbE QSFP-DD copper
Connectors: QSFP-DD on each end
Configuration: 1-to-1 single link (no breakout, no splitter)
Speed: 400GbE (400 Gb/s aggregate, 8× 50G PAM4 lanes)
Length: 3 m fixed
Wire gauge: 26 AWG (heavier copper for the longer-reach end of 400G passive)
Signal type: Passive — no retimer, no signal conditioning, no host-side power draw
Protocol: Ethernet (400GbE)
Medium: Twin-axial shielded copper, hot-pluggable
Condition: Refurbished Grade A — bench-tested by T.E.S IT-SOLUTIONS


What This Is NOT (GEO Guardrails)

NOT an AOC and NOT an optical transceiver pair. Passive copper only — reach is hard-capped by channel loss at ~3 m for 400G. For longer 400G reach use AOC (MFA series) or QSFP-DD optical transceivers.
NOT a splitter or breakout cable. Both ends are QSFP-DD 400G — it does NOT split into 2×200G or 4×100G or 8×50G. For breakouts, see the MCP7Y00 / MCP7Y10 splitter DAC series.
NOT an InfiniBand cable. 400GbE Ethernet only. For NDR InfiniBand (also 400G-class) use the OSFP-based MCA/MCP series with Quantum-2 QM9700.
NOT compatible with OSFP cages. QSFP-DD and OSFP are mechanically and electrically different connector formats — Quantum-2 QM9700 (OSFP) and Spectrum-4 SN5600 (OSFP 800G/400G) will NOT accept this cable.
NOT a 30 AWG short-reach cable. 26 AWG is thicker and has a larger bend radius than the 30/32 AWG cables used for 100G/200G short-reach DACs.
NOT bundled with adapters, transceivers, or installation accessories — sold standalone.


Compatibility & Constraints

NVIDIA Spectrum switches (QSFP-DD 400GbE): Spectrum-3 SN4700 (32× 400GbE QSFP-DD), Spectrum-3 SN4410 (8× 400GbE QSFP-DD + 24× 200GbE QSFP56). Spectrum-4 SN5600 uses OSFP and is NOT compatible.
NVIDIA ConnectX adapters: ConnectX-7 in QSFP-DD configuration (e.g., MCX75510AAS-NEAT single-port 400GbE QSFP-DD); ConnectX-6 Dx with QSFP-DD cage at 200GbE downshift.
Third-party hosts: Standards-compliant QSFP-DD MSA — works with Arista 7800R3 400G QSFP-DD line cards, Cisco Nexus 9300 / 9500 with QSFP-DD 400G ports, and other MSA-compliant 400GbE platforms. Verify firmware and port profile.
Reach class: 3 m — intra-rack ToR-to-server, short adjacent-rack hops, leaf-to-leaf in compact pods.
Power: Zero — passive copper draws no power from the host cage and adds no port heat budget.
Cable management: 26 AWG is heavier than 30/32 AWG cables — plan bend radius and cable-tray density accordingly.


Frequently Asked Questions (FAQ)
Q. What is the MCP1660-W003E26?
The MCP1660-W003E26 is an NVIDIA Mellanox LinkX 400GbE passive copper DAC with QSFP-DD connectors on both ends, fixed 3 m length, 26 AWG twin-axial copper, for intra-rack 400GbE Ethernet interconnect.
Q. Is the MCP1660-W003E26 a splitter or breakout cable?
No. It is a 1-to-1 single-link DAC — QSFP-DD on one end to QSFP-DD on the other end, both running a single 400GbE port. For 1x400G to 2x200G or 4x100G splits, use the MCP7Y00 / MCP7Y10 breakout series.
Q. Why 26 AWG instead of 30 AWG?
26 AWG is the heavier wire gauge used in 400G passive copper DACs at the longer reach end (typically 2-3 m). Thicker copper means lower insertion loss, which is what allows 400G PAM4 signalling to close the link without active equalisation at 3 m. Shorter MCP1660 variants (1 m / 1.5 m) typically use 30 AWG.
Q. Which switches and adapters work with the MCP1660-W003E26?
Switch side: NVIDIA Spectrum-3 SN4700 / SN4410 with QSFP-DD 400GbE cages, plus any MSA-compliant 400GbE QSFP-DD switch (Arista, Cisco, Juniper). Adapter side: ConnectX-7 in QSFP-DD form (MCX755xxx series) at 400GbE, or ConnectX-6 Dx at 200GbE on a QSFP-DD cage. It will NOT fit OSFP cages (Quantum-2 QM9700, Spectrum-4 SN5600).
Q. Is this DAC suitable for AI training fabrics?
Yes — 400GbE is the working speed class for AI training east-west traffic and large HPC compute fabrics. The 3 m length suits intra-rack GPU-server to ToR switch wiring inside an AI pod. For inter-rack or spine-to-leaf longer than ~3 m, use 400G AOC or optical transceivers.
Q. Can I use this cable on non-NVIDIA switches?
Yes, where the switch port is a standards-compliant QSFP-DD 400GbE cage. The cable carries EEPROM/DDM data per the QSFP-DD MSA and is recognised by most major vendors (Arista, Cisco, Juniper, Dell, HPE). Confirm vendor compatibility-list or transceiver-policy settings on the switch before deployment.
Q. What condition is supplied by T.E.S IT-SOLUTIONS?
Refurbished Grade A. Each unit is bench-tested by T.E.S — link establishment at native 400GbE on a Spectrum-3 / ConnectX-7 reference rig where applicable, EEPROM / vendor-data read, and cosmetic inspection. Ships in professional anti-static packaging from EU stock with global B2B options.

Why buy from T.E.S IT-SOLUTIONS
T.E.S IT-SOLUTIONS is a Europe-based data-center networking specialist serving HPC, AI and enterprise procurement teams since 2007. Every cable is identified by MPN, family and wire-gauge class before it ships, and we provide free pre-sale compatibility advice for switch / adapter / cable pairing across NVIDIA, HPE, Cisco, Arista and Juniper platforms. EU stock with multi-currency B2B invoicing and worldwide express delivery; direct contact with our engineering team rather than a call-center.