Mariam Elgamal

The world’s push toward an environmentally sustainable society is highly dependent on the semiconductor industry. Despite existing carbon modeling efforts to quantify carbon footprint of computing systems, optimizing carbon footprint in large design spaces-while also considering trade-offs in power, performance, and area-is especially challenging. To address this need, we present CORDOBA, a carbon-aware optimization framework that optimizes carbon efficiency. We quantify carbon efficiency using the total Carbon Delay Product metric (tCDP): the product of total carbon and application execution time. We justify why tCDP is an effective metric for quantifying carbon efficiency. We use CORDOBA to explore the large design space for carbonefficient specialized hardware, and identify distinct carbonefficient optimal designs across operational use (eliminating up to 98% of the design space) despite uncertainty in carbon footprint parameters. We quantify opportunities to improve tCDP for real system case studies: (a) optimizing hardware provisioning from 8 to 4 cores in real system CPUs improves tCDP by 1.25×; and (b) leveraging advanced three-dimensional (3D) integration techniques (3D stacking of separately-fabricated logic and memory chips) improves tCDP by 6.9× versus conventional systems.

Given the performance and efficiency optimizations realized by the computer systems and architecture community over the last decades, the dominating source of computing’s carbon footprint is shifting from operational emissions to embodied emissions. These embodied emissions owe to hardware manufacturing and infrastructure-related activities. Despite the rising embodied emissions, there is a distinct lack of architectural modeling tools to quantify and optimize the end-to-end carbon footprint of computing. This work proposes ACT, an architectural carbon footprint modeling framework, to enable carbon characterization and sustainability-driven early design space exploration. Using ACT we demonstrate optimizing hardware for carbon yields distinct solutions compared to optimizing for performance and efficiency. We construct use cases, based on the three tenets of sustainable design—Reduce, Reuse, Recycle—to highlight future methods that enable strong performance and efficiency scaling in an environmentally sustainable manner.