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Power and Performance Evaluation of Globally Asynchronous, Locally Synchronous Processors

April 30, 2002 Tuesday
Hamerschlag Hall 1112
4:00 p.m.

Diana Marculescu

Assistant Professor, Dept. of ECE, CMU

Due to increasing clock speeds, increasing design sizes and shrinking technologies, it is becoming more and more challenging to distribute a single global clock throughout a chip. In this talk, I will discuss the effect of using a Globally Asynchronous Locally Synchronous (GALS) organization for a superscalar, out-of-order processor, both in terms of power and performance. To this end, we propose a novel modeling and simulation environment for multiple clock cores with static or dynamically variable voltages for each synchronous block. Using this design exploration environment we were able to assess the power/performance trade-offs available for Multiple Clock, Single Voltage (MCSV), as well as Multiple Clock, Multiple Voltage (MCMV) cores. Our results show that MCSV processors can be more power efficient than their fully synchronous counterparts, at the expense of an average 8% performance degradation. However, in some cases, the extra execution time translates into more power consumption, thus offsetting the power benefits of a global clockless design. On the other hand, for some applications, a MCMV design can provide more than 20% total energy savings with less than 7% performance reduction when compared to the fully synchronous core. I will conclude the talk with possible directions for future research and applications of GALS in multiple speed/multiple voltage pipelines.

Diana Marculescu is an Assistant Professor of ECE at Carnegie Mellon University. She has received her Ph.D. in Computer Engineering in 1998 from University of Southern California and her M.S. in Computer Science from "Politehnica" University of Bucharest in 1991. Diana Marculescu is a recipient of a NSF Career Award (2000) and a member of the organizing committee of the ACM/IEEE Intl. Symposium on Low Power Electronics and Design. She also serves on the technical program committee of several conferences, including IEEE/ACM Intl. Conference on Computer-Aided Design and IEEE Design, Automation and Test in Europe Conference. Her research interests are in the area of energy aware computing, VLSI, computer architecture and CAD for power modeling and estimation.


Department of Electrical and Computer EngineeringCarnegie Mellon UniversitySchool of Computer Science