Nvidia Reveals 51Tbps Ethernet Switch

Due to sample late this year, Spectrum-4 will quadruple the bandwidth of

Spectrum-3 by both doubling per-lane speed to 100Gbps and doubling the

number of serdes lanes to 512, yielding 51.2Tbps.

Bob Wheeler

About two years after completing the Mellanox acquisition, Nvidia announced Spectrum-4, its next-

generation Ethernet-switch ASIC. We use the term ASIC because unlike Broadcom and Marvell, Nvidia will

sell the chip only in its own system-level products. Spectrum-4 will quadruple the bandwidth of Spectrum-3

by both doubling per-lane data rate to 100Gbps and doubling the number of serdes lanes to 512, yielding

51.2Tbps. Nvidia will build this 100-billion-transistor chip in the same TSMC 4nm process as its Hopper GPU,

targeting air-cooled system designs. Samples are due late this year, followed by production systems in early

2023.

Spectrum-4 will handle 128x400G or 256x200G-and-below standard Ethernet ports, and it’ll also support

64x800G ports using the Ethernet Technology Consortium’s 800G specification, an industry ad hoc standard.

Nvidia says its 112Gbps PAM4 serdes will drive copper (DAC) cabling up to 1.5m, avoiding the added cost

and power of active cables in a rack. The chip’s undisclosed number of packet-processing pipelines handle

an aggregate 37.6 billion packets per second into and out of a fully shared packet buffer. One-quarter of its

ports perform MACSec encryption, allowing protection for up to 12.8Tbps of tunneled traffic (using VXLAN).

For out-of-band management and configuration, the ASIC includes two 25G Ethernet ports and a PCIe Gen4

x4 host interface.