1 / 16

Power-Aware Computing 101

Power-Aware Computing 101. CS 771 – Optimizing Compilers Fall 2005 – Lecture 22. Today. Quick intro to power-aware computing Special thanks to David Brooks! Paper discussion Heath et al., "Code Transformations for Energy-Efficient Device Management", 2004.

derry
Download Presentation

Power-Aware Computing 101

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Power-Aware Computing 101 CS 771 – Optimizing Compilers Fall 2005 – Lecture 22

  2. Today • Quick intro to power-aware computing • Special thanks to David Brooks! • Paper discussion • Heath et al., "Code Transformations for Energy-Efficient Device Management", 2004. • Hsu and Kremer, "The Design, Implementation, and Evaluation of a Compiler Algorithm for CPU Energy Reduction", 2003. CS 771, Fall 2005

  3. Battery life Thermal issues: affect cooling, packaging, reliability, timing Environment Why Worry about Power Dissipation? CS 771, Fall 2005

  4. Nuclear Reactor Pentium 4 (Prescott) Pentium 4 Hot Plate Pentium 3 Pentium 2 Pentium Pro Pentium 486 386 Power Dissipation Trends CS 771, Fall 2005

  5. Cooking-Aware Computing CS 771, Fall 2005

  6. Where Does the Juice Go in Laptops? CS 771, Fall 2005

  7. Environment • Environment Protection Agency (EPA): computers consume 10% of commercial electricity consumption • This incl. peripherals, possibly also manufacturing • A DOE report suggested this percentage is much lower (3.0-3.5%) • No consensus, but it’s still a lot • Interesting to look at the numbers: • http://enduse.lbl.gov/projects/infotech.html • Data center growth was cited as a contribution to the 2000/2001 California Energy Crisis • Equivalent power (with only 30% efficiency) for AC • CFCs used for refrigeration • Lap burn • Fan noise CS 771, Fall 2005

  8. Now We Know Why Power is Important • What can we do about it? • Two components to the problem: • #1: Understand where and why power is dissipated • #2: Think about ways to reduce it at all levels of computing hierarchy • In the past, #1 is difficult to accomplish except at the circuit level • Consequently most low-power efforts were all circuit related CS 771, Fall 2005

  9. Power: The Basics • Dynamic “switching” power vs. Static “leakage” power • Dynamic power dominates, but static power increasing in importance • Trends in each • Static power: steady, per-cycle energy cost • Dynamic power: capacitive and short-circuit • Capacitive power: charging/discharging at transitions from 01 and 10 • Short-circuit power: power due to brief short-circuit current during transitions. • Most research focuses on capacitive, but recent work on others CS 771, Fall 2005

  10. Vdd 20 cycles Vin Vout CL Minimum Voltage Power Issues in Microprocessors Capacitive (Dynamic) Power Static (Leakage) Power Di/Dt (Vdd/Gnd Bounce) Temperature Current (A) Voltage (V) CS 771, Fall 2005

  11. Capacitance: Function of wire length, transistor size Supply Voltage: Has been dropping with successive fab generations Clock frequency: Increasing… Activity factor: How often, on average, do wires switch? Capacitive Power Dissipation Power ~ ½ CV2Af CS 771, Fall 2005

  12. Lowering Dynamic Power • Reducing Vdd has a quadratic effect • Has a negative (~linear) effect on performance however • Lowering CL • May improve performance as well • Keep transistors small (keeps intrinsic capacitance (gate and diffusion) small) • Reduce switching activity • A function of signal transition stats and clock rate • Clock gating idle units • Impacted by logic and architecture decisions CS 771, Fall 2005

  13. Power vs. Energy CS 771, Fall 2005

  14. Power vs. Energy • Power consumption in watts • Determines battery life in hours • Sets packaging limits • Energy efficiency in joules • Rate at which energy is consumed over time • Energy = power * delay (joules = watts * seconds) • Lower energy number means less power to perform a computation at same frequency CS 771, Fall 2005

  15. Power vs. Energy Metrics • Power-delay Product (PDP) = Pavg * t • PDP is the average energy consumed per switching event • Energy-delay Product (EDP) = PDP * t • Takes into account that one can trade increased delay for lower energy/operation • Energy-delay2 Product (EDDP) = EDP * t • Why do we need so many formulas?!!? • We want a voltage-invariant efficiency metric! Why? • Power ~ ½ CV2Af, Performance ~ f (and V) CS 771, Fall 2005

  16. On to the Discussion… • Heath et al., "Code Transformations for Energy-Efficient Device Management", 2004. • Hsu and Kremer, "The Design, Implementation, and Evaluation of a Compiler Algorithm for CPU Energy Reduction", 2003. CS 771, Fall 2005

More Related