CSC 714 Project
Power-Aware DVFS on PowerPC 405LP: Front Bus Scaling 

Project Team:
Mohamed Nishar Kamaruddin (mkamaru@ncsu.edu)
Santhosh Selvaraj (sselvar@ncsu.edu)

Overview:

Power management is an important design aspect of embedded systems design, especially for battery constrained devices. Various power optimization techniques have been proposed which offer power reduction while maintaining the safe operation of the system. Many processors support different power saving modes, but they involve lot of overhead for hard real-time systems. Recently many processors added support for Dynamic Power Management (DPM) techniques which allow power parameters to be changed even while a program is in execution.

 

Dynamic Voltage Scaling (DVS) and Dynamic Frequency Scaling (DFS) are the most widely deployed DPM techniques. But dynamic power management techniques when applied only to processor core can be of limited use. Latest technological advances in processor design has lead to the development of low-power processor cores. Power optimization on the already low power consuming processor core might not provide significant power savings. Internal/external bus and memory also consume significant power, sometimes even more than the processor itself. So voltage and frequency scaling can be expected to provide significant power optimization when applied to the internal/external bus and memory subsystem. The aim of this project would be to integrate DVS/DFS to the front side bus and memory subsystem and study the power optimizations that can be achieved on the IBM PowerPC 405LP board.


Project Status:
Task Details Status
Study of the IBM PowerPC 405LP board and development environment. Completed
Study Comedi drivers under Linux to obtain the voltage/current measurements from the acquisition board for the memory subsystem Completed
Understand the DPM module of the MontaVista Linux RTOS and learn how to set/change frequency for the front side bus and the memory subsystem. Completed
Understand the implementation of the existing PID feedback controller so that it can be implemented for the memory subsystem Completed
Integration of PLB scaling mechanism with the existing EDF-based DVS scheduler Completed
Documentation of current and voltage measurements of the memory subsystem for further study Completed

Deliverables:

March 16, 2009: Project Proposal Submitted (pdf)
April 01, 2009: Intermediate Project Report Submitted (pdf)
April 20, 2009: Project Presentation Slides Submitted (ppt)
April 21, 2009: Final Report Submitted (pdf)
April 21, 2009: Source Code Submitted (zip)

References:
  1. A survey of design techniques for system-level dynamic power management by Benini, L.; Bogliolo, A.; De Micheli, G. Very Large Scale Integration (VLSI) Systems, IEEE Transactions

  2. Dynamic Power Management for Embedded Systems, IBM and MontaVista Software

  3. System level power-performance trade-offs in embedded systems using voltage and frequency scaling of off-chip buses and memory(2002) by Kiran Puttaswamy, Kyu-won Choi, Jun Cheol Park, Vincent J. Mooney Iii, Abhijit Chatterjee, Peeter Ellervee. In Proceedings of International Symposium on System Synthesis (ISSS’02)

  4. Exploiting Synchronous and Asynchronous DVS for Feedback EDF Scheduling on an Embedded Platform by Y. Zhu and F. Mueller in ACM Transactions on Embedded Computing Systems, Vol. 7, No. 1, Dec 2007, Pages 1-26.

  5. Feedback EDF Scheduling of Real-Time Tasks Exploiting Dynamic Voltage Scaling by Y. Zhu and F. Mueller in Real-Time Systems Journal, Vol. 31, No. 1-3, Dec 2005, Pages 33-63.

  6. Power reduction techniques for microprocessor systems ACM Computing Surveys (CSUR) Volume 37, Issue 3 (September 2005) Pages: 195 - 237
  7. PowerPC 405 User Manual
  8. Comedi Documentation