Thesis Title: LongLiveNoC: Wear Levelling, Write Reduction and Selective VC allocation for Long lasting Dark Silicon aware NoC Interconnects

Increasing processing demand has led to the development of chip multiprocessors which can have multiple to many cores connected with each other and with the on-chip caches. These connections are established by an on-chip packet-switched Network-on-Chip (NoC). Scaling of technology nodes increases the power dissipated by the chips leading to thermal restrictions. To control the chip thermal design power, certain components (like cores and caches) may be turned off. However, in this scenario of dark silicon, the interconnect is expected to be available.

The thesis aims to save power consumed by this always ON interconnect by replacing the power-hungry SRAM buffers in the routers with low leakage Non-Volatile Memory (NVM) based buffers. However, the major challenges with the employment of the NVMs are slower writes and weak write endurance.

The thesis proposes:
1. Methods to evenly distribute the writes across these NVM buffers in order to increase their lifetime. This is done by static and dynamic allocation of buffers to the virtual channels and their selection during packet transmission.

2. Power can also be saved by using frequency scaling of the routers and/or turning off certain buffers when the usage is less. The investigation is done for all such approaches and power savings are demonstrated.

3. Endurance can be improved and energy can be saved if we can reduce the number of writes performed on the buffers. This is achieved by proposing two compression techniques leading to reduced network traffic and improved lifetime.

All the above methods help in improving the lifetime of the NVM based NoC interconnects in the context of dark silicon.

Sandhya Dwarkadas is the Walter N. Munster Professor and Chair of Computer Science at the University of Virginia. Previously, she was the Albert Arendt Hopeman Professor of Engineering at the University of Rochester, where she was professor of computer science with a secondary appointment in electrical and computer engineering, and also served as department chair for 6 years. She received the 2020 Edmund A. Hajim Outstanding Faculty Award from the University of Rochester. She received her Bachelor’s degree from the Indian Institute of Technology, Madras, India, and her M.S. and Ph.D. from Rice University. She is a fellow of the ACM and IEEE. She was co-chair of the CRA-WP board and steering committee from 2019-2022 and has been on the CRA-WP board since 2010.
Her areas of research interest include parallel and distributed computing, computer architecture, and the interaction and interface between the compiler, runtime/operating system, and underlying architecture. She has made fundamental contributions to the design and implementation of shared memory both in hardware and in software, and to hardware and software energy- and resource-aware configurability.

Since 2014, I am an Associate Professor at the Education and Research Department of Computer Science and Electrical Engineering in University of Rennes 1, whereas my research activities are taking place at the IRISA/INRIA Rennes Bretagne Atlantique research center. My research interests include Embedded Systems, Real-time Systems, Mixed-Critical Systems, Hardware/Software Co-design, Mapping Methodologies, Design Space Exploration Methodologies, Memory Management Methodologies, Low Power Design, Fault Tolerance.

Mary Jane (Janie) Irwin is an Emerita Evan Pugh University Professor in the Department of Computer Science and Engineering at The Pennsylvania State University. She retired in July 2017. Her research and teaching interests include computer architecture, energy-aware and reliability-aware design, emerging technologies, and VLSI systems design and design automation. She is a Fellow of IEEE and ACM and a member of NAE and AAAS. Awards she has received include the 2003 IEEE/CAS VLSI Transactions Best Paper of the Year Award, the 2010 ACM Athena Lecturer Award, the 2012 Ten-Year Retrospective Most Influential ASP-DAC Paper Award, the 2015 FLP Conference 25 Year Paper Recognition, the 2017 ACM/SIGDA Pioneering Achievement Award, and the 2018 EDAA Lifetime Achievement Award. Irwin received her M.S. and Ph.D. degrees from the University of Illinois, Urbana-Champaign and an Honorary Doctorate from Chalmers University, Sweden.htt