NVIDIA Mellanox MCP1660-W00A 400GbE QSFP-DD DAC, 0.5m: This is a 0.5-meter passive Direct Attach Copper (DAC) cable for in-rack 400GbE Ethernet connections. The cable terminates in QSFP-DD connectors at both ends and is rated to IEEE 802.3cd. This is a passive electrical assembly with 30AWG copper conductors and an LSZH jacket; it contains no transceivers, retimers, or active components. This is a new factory unit.
Engineering Context
The MCP1660-W00A delivers 400Gb/s Ethernet over 8 lanes of 50Gb/s PAM4 modulation in the QSFP-DD form factor. At 0.5m, it is the shortest reach in the 400GbE DAC family, optimized for adjacent rack-unit ToR-to-server runs and intra-chassis interconnects. As a passive copper assembly it consumes 0W and introduces near-zero electrical latency compared to AOC or transceiver-based alternatives. The 30AWG conductors and short reach provide signal-integrity headroom for PAM4 at 50Gb/s per lane.
Deployment & Use Cases
400GbE Ethernet uplinks from Spectrum-3 (SN4000 series) or Spectrum-4 (SN5000 series) ToR switches to adjacent ConnectX-7 hosts. In-rack short interconnects between adjacent rack-units, including switch-to-switch stacking and aggregator pairings. Cost-optimized 400GbE deployments where 0.5m reach is sufficient and AOC budget is not justified.
Technical Specifications
OEM: NVIDIA Mellanox
Part Number: MCP1660-W00A
NVIDIA P/N Reference: 980-9I35R-00W00A
Form Factor: QSFP-DD to QSFP-DD
Data Rate: 400GbE (8x 50Gb/s PAM4)
Cable Type: Passive Copper DAC
Length: 0.5m
Gauge: 30AWG
Jacket: LSZH
Standard: IEEE 802.3cd
Power Consumption: 0W (passive)
Condition: New
Compatibility & Constraints
Compatible with NVIDIA Spectrum-3 (SN4000 series) and Spectrum-4 (SN5000 series) Ethernet switches and ConnectX-7 adapters configured for 400GbE QSFP-DD operation. The host port must support 8x 50Gb/s PAM4 signaling and IEEE 802.3cd. Not compatible with QSFP56 (HDR/200GbE) or QSFP28 (100GbE) ports — QSFP-DD has eight electrical lanes versus four. Not for InfiniBand: this is an Ethernet-only DAC.
Frequently Asked Questions (FAQ)
Q. What is the MCP1660-W00A?
The MCP1660-W00A is a 0.5m passive copper DAC with QSFP-DD connectors on both ends, rated for 400GbE Ethernet.
Q. Is this a splitter cable?
No. It is a straight 1-to-1 QSFP-DD-to-QSFP-DD point-to-point assembly.
Q. Will T.E.S IT-SOLUTIONS confirm the configuration of MCP1660-W00A before shipping?
Yes. T.E.S IT-SOLUTIONS (tes-itsolutions.com) bench-tests each unit where test topology is available, before dispatch from EU stock.

Why Choose T.E.S IT-SOLUTIONS
T.E.S IT-SOLUTIONS tests every 400GbE DAC for conductor continuity, connector seating, and 400GbE link training prior to shipment. Our team provides expert consultation on Spectrum-3/4 fabric design, 1–3 day handling, and global shipping. Visit the product page for details and warranty information.