Posted: June 10, 2021
While power consumption has always been an important metric for switch/router silicon, it is quickly becoming one of the most critical factors in network system design. Over the last decade, power consumption has progressed from factors related mainly to cost to a deciding factor on whether new network equipment can be deployed at all — considering infrastructure and rack-level power supply or cooling limitations. For example, IT managers are now asking themselves, “Will I have to use a heat sink or what type of fan will I need?” Recognizing the importance of power efficiency, Broadcom has been at the forefront of low power network silicon design and has consistently led the industry in terms of throughput per watt.
A good example of what has been achieved in successive generations of Broadcom silicon can be seen in the evolution of the high-end data center switch chips, as shown in the figure below.
Over the past 10 years, Broadcom switch silicon has increased in bandwidth by a factor of 40x. The 640Gbps Trident switch had a typical power consumption of 65W or 102W/Tbps. The latest Tomahawk4 switch, the world’s only shipping product at 25.6Tbps, has a typical power consumption of 310W, or 12W/Tbps. This is almost a 90 percent improvement in power efficiency.
There are three main factors that contribute to power efficiency in networking silicon: architecture, process technology and physical design.
Choice of architecture is the largest lever in optimizing power. There’s been much focus recently about application-specific architectures dominating the next wave of compute silicon. Most times during these discussions, people fail to understand that this trend has already been in place for networking silicon. Broadcom has three application-specific switch/router architectures — Tomahawk, Trident and Jericho — that were optimized for specific network needs. Alternative approaches, such as NPU-style run-to-completion engines, which try to span multiple applications with one architecture, inherently have higher power consumption.
The advantages of leading-edge process technology and low-power IP are well known factors in minimizing power consumption. Broadcom has consistently led the industry in adopting the latest process technologies. The Broadcom Trident 4, for example, was the industry’s first switch/router silicon implemented in 7nm. Broadcom also leads the industry in providing low-power IP, including a wide variety of memory instances specifically optimized for the tables and buffers required for switching and routing, as well as SerDes specifically designed for ultra-high port count ASICs.
Finally, physical design, the ability to translate an architecture into a fully optimized collection of transistors and wires, is the last remaining factor in providing the lowest power. Broadcom is well known for its execution capabilities, consistently bringing the highest-end switch/router silicon to market before any of its peers. This execution capability includes physical design techniques that minimize power: incorporating a wide-variety of optimized SRAMs and TCAMs, extensive clock gating, low-power standard cells, tools and frequency selection to minimize supply voltages and the number of low-Vt transistors, among other factors. As the saying goes, there’s no compression algorithm for experience. This is certainly true for extremely complex networking silicon containing hundreds of SerDes and billions of transistors.
As the networking industry continues its inexorable path toward higher bandwidths and increased systems densities, power efficiency is playing an increasingly important role. Customers can be assured that Broadcom will continue its focus on providing application-specific architectures implemented with the most advanced process technology and the most efficient physical design, allowing them to deploy the world’s most power-efficient networking devices.
