While I/O speeds continue increasing, they’re still not keeping pace with compute power. What’s happening is, as Moore’s law slows and the laws of semiconductor physics waver, a gap is widening between compute power and I/O bandwidth. To increase compute resources, more transistors can be added to a chip (and multi-die systems present an opportunity to add even more transistors to scale compute power. Techniques such as parallelizing CPUs and multi-threading also increase system performance. But I/O performance has increased by less than five percent as logic density has doubled and, since the emergence of 45nm process technology, costs per mm2 have continued increasing. Given the volume and complexity of today’s data, the I/Os are becoming the bottleneck.
To support our unrelenting demands for data, hyperscale data centers are moving to network architectures that are faster, flatter, and more scalable. A flatter architecture of no more than three layers of switches lowers latency and drives up the need for higher bandwidth and efficient connectivity over longer distances. Answering the connectivity call is the Ethernet high-speed interface, long considered the data connectivity backbone for the internet.
Each generation of the Ethernet standard has delivered double the speed, addressing the demands of an increasingly hyper-connected world. In fact, hyperscalers have become big influencers of the Ethernet roadmap, driving the evolution toward 1.6T. Historically, revisions of interface standards have taken place every four years; these days, that rate is reducing to address the I/O bandwidth gap.
The Ethernet protocol also provides a level of flexibility that is appealing for data center SoC designers, from speed negotiation to backwards compatibility with the software stack to the ability to use different kinds and classes of media. Optical fiber, copper cables, and PCB backplanes are all supported. Being able to use optical fiber connections is particularly enticing to prevent the I/O bottleneck, as copper cables are starting to run out of steam to support increasing networking speeds.