Tomahawk 5 Switches At 51.2Tbps

Broadcom is the first vendor to sample a 51Tbps data-center switch chip. The 5nm device features 100Gbps serdes and port speeds of up to 800G Ethernet.

Joseph Byrne

Oops, Broadcom did it again. One more time, the company has doubled data-center switching performance. Employing the same number of PAM4 serdes as its predecessor but running them twice as fast, the new Tomahawk 5 (BCM78900) delivers double the throughput and supports 800G Ethernet (800GbE). Facing heightened competition from rivals, Broadcom is sampling it now, just ahead of Nvidia’s similar Spectrum-4 switch. We expect the new chip to qualify for production by the end of 2023.

Tomahawk 5 is the company’s first 5nm merchant switch IC and its first product to support 800GbE. We estimate power consumption increases only 10% over the 7nm Tomahawk 4, reaching 500W. Once unheard of, a half-kilowatt chip is nonetheless fit for air-cooled systems. Like its predecessors, Tomahawk 5 is monolithic, avoiding the power penalty of chiplet-based architectures.

Overall switching throughput is 51.2Tbps, permitting 64x800GbE, 128x400GbE, and 256x200GbE configurations. A typical 800GbE optical-module standard is the OSFP MSA, which also allows dual-400GbE and single-800GbE configurations. In addition, Tomahawk 5 improves direct-attach-copper (DAC) support and comes in a model integrating copackaged optics for all ports.

Broadcom aims Tomahawk mainly at fixed-port data-center switches, whereas the Trident and Jericho lines target enterprise and service-provider switches. Trident is more flexible: it handles more protocols, has bigger access-control lists, and is customer programmable. To enable big, high-speed systems, Jericho has deeper packet buffers. That specialization allows Broadcom to streamline Tomahawk and maximize throughput.