The NVIDIA/Mellanox Cable is an 400Gb/s twin-port OSFP to four 100Gb/s QSFP56 InfiniBand HDR Direct Attached Copper quad breakout cable. The 8-channel twin-port OSFP end uses a IHS/Finned Top form-factor for use in Quantum-2 and Spectrum-4 switch cages. The four 100G ends support 2-channels of 50G-PAM4 (100GbE/HDR100) and use a RHS/Flat Top QSFP56 for use in ConnectX-6/7 adapters and BlueField-2/3 DPUs using riding heat sinks on the connector cage. This cable is compliant with OSFP MSA (Multi-Source Agreement) and IEEE 802.3cd standards.
DACs offer the lowest latency, so are widely used in data centers to connect servers and GPU compute systems to the top-of-rack (TOR) switches and link spine-to-super-spine switches inside racks over short cable lengths. DACs are also used to create InfiniBand storage fabrics with hard-disk-drive (HDD) and flash memory subsystems.
Featuring a simple design and minimal components, DAC cables offer the lowest-cost, lowest-latency, and near-zero-power connections for high-speed links. They enhance port bandwidth, density, configurability, and reduce power requirements in supercomputers and hyperscale systems.
Note："Finned-top" transceivers are now called "Integrated Heat Sink" (IHS) as the cooling fins are integrated into the OSFP connector metal top. Commonly used in air-cooled switches. "Flat-top" transceivers are now called "Riding Heat Sink" (RHS) as the cooling fins ride on top of the network card or systems internal cages. This is used for both air-cooled and liquid-cooled applications for DGX, ConnectX-7 and BlueField-3 DPUS.
