L15 Power

L15 Power - Power 6.371 Fall 2002 10/25/02 L15 Power 1 1000...

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L15 – Power 1 6.371 – Fall 2002 10/25/02 Power
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L15 – Power 2 6.371 – Fall 2002 10/25/02 Power Trends ± CMOS originally used for very low-power circuitry such as wristwatches ± Now some CPUs have power dissipation >100W 0.1 1 10 100 1000 1970 1980 1990 2000 2010 2020 Power (Watts) 8080 8086 386 Pentium® proc Pentium® 4 proc [ Source: Intel ] 1000W CPU?
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L15 – Power 3 6.371 – Fall 2002 10/25/02 Itanium Temperature Plot Execution core 120 o C Cache 70°C Integer & FP ALUs Temp ( o C) [ Source: Intel ]
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L15 – Power 4 6.371 – Fall 2002 10/25/02 Power Concerns ± Power dissipation is limiting factor in many systems battery weight and life for portable devices packaging and cooling costs for tethered systems case temperature for laptop/wearable computers fan noise not acceptable in some settings ± Internet data center, ~8,000 servers,~2MW 25% of running cost is in electricity supply for supplying power and running air-conditioning to remove heat ± Environmental concerns ~2003, 1 billion PCs, 100W each => 100 GW 100 GW = 40 Hoover Dams
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L15 – Power 5 6.371 – Fall 2002 10/25/02 Power Dissipation in CMOS Primary Components: ± Capacitor charging, energy is ½CV 2 per transition ² the dominant source of power dissipation today ± Short-circuit current, PMOS & NMOS both on during transition ² kept to <10% of capacitor charging current by making edges fast ± Subthreshold leakage, transistors don’t turn off completely ² approaching 10-30% active power in <180nm technologies ± Diode leakage from parasitic source and drain diodes ² usually negligible ± Gate leakage from electrons tunneling across gate oxide ² was negligible, increasing due to very thin gate oxides C L Diode Leakage Current Subthreshold Leakage Current Short-Circuit Current Capacitor Charging Current Gate Leakage Current
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L15 – Power 6 6.371 – Fall 2002 10/25/02 Energy to Charge Capacitor ± During 0->1 transition, energy C L V DD 2 removed from power supply ± After transition, ½ C L V DD 2 stored in capacitor, the other ½ C L V DD 2 was dissipated as heat in pullup resistance ± The ½ C L V DD 2
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This note was uploaded on 08/23/2009 for the course EECS 6.371 taught by Professor Krsteasanovic during the Fall '02 term at MIT.

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L15 Power - Power 6.371 Fall 2002 10/25/02 L15 Power 1 1000...

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