Google's Training Supercomputers from TPU v2 to Ironwood: Architectural Stability, Scale, Resilience, Power Efficiency, and Sustainability Across Five Generation

This paper provides an overview of Google's TPUs across five generations, from TPU v2 to Ironwood, highlighting their evolution as scalable, resilient, and sustainable supercomputers for AI training. It details the TPU’s stable architecture and microarchitecture, which has surprisingly easily accommodated the rapidly changing deep neural network workloads, such as the rise of Transformers. Key advancements over eight years include 10x increase in HBM capacity and bandwidth per node, a 100x increase in peak node performance, and a 3600x increase in supercomputer performance. The paper also discusses the role of optical circuit switches and built-in self test in enhancing resilience, how TPU’s carbon footprint was reduced by improving embodied carbon emissions per floating point operation and a 30x gain in performance per Watt. It concludes by identifying six features that may well characterize the successful AI accelerators of this decade.

• Machine intelligence