12_power

12_power - Readings Textbook(MA:FSPTCM Section 9.1 CIS 501...

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CIS 501 (Martin): Power 1 CIS 501 Computer Architecture Unit 12: (Low) Power and Energy Slides originally developed by Amir Roth with contributions by Milo Martin at University of Pennsylvania with sources that included University of Wisconsin slides by Mark Hill, Guri Sohi, Jim Smith, and David Wood. Readings • Textbook (MA:FSPTCM) Section 9.1 CIS 501 (Martin): Power 2 CIS 501 (Martin): Power 3 Power/Energy Are Increasingly Important Battery life for mobile devices • Laptops, phones, cameras Tolerable temperature for devices without active cooling • Power means temperature, active cooling means cost • No room for a fan in a cell phone, no market for a hot cell phone Electric bill for compute/data centers • Pay for power twice: once in, once out (to cool) Environmental concerns • “Computers” account for growing fraction of energy consumption Energy & Power Energy : measured in Joules or Watt-seconds • Total amount of energy stored/used • Battery life, electric bill, environmental impact • Instructions per Joule (car analogy: miles per gallon) Power : energy per unit time (measured in Watts) • Related to “performance” (which is also a “per unit time” metric) • Power impacts power supply and cooling requirements (cost) • Power-density (Watt/mm 2 ): important related metric • Peak power vs average power • E.g., camera, power “spikes” when you actually take a picture • Joules per second (car analogy: gallons per hour) • Two sources: Dynamic power : active switching of transistors Static power : leakage of transistors even while inactive CIS 501 (Martin): Power 4

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CIS 501 (Martin): Power 5 Dynamic Power
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12_power - Readings Textbook(MA:FSPTCM Section 9.1 CIS 501...

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