CS 250 VLSI System Design Lecture 5 Power and Energy 2009 9 10 John Wawrzynek and Krste Asanovic with John Lazzaro TA Yunsup Lee www inst eecs berkeley edu cs250 CS 250 L5 Power and Energy UC Regents Fall 2009 UCB 1 Sad fact Computers turn electrical energy into heat Computation is a byproduct Energy and Performance Air or water carries heat away or chip melts CS 250 L5 Power and Energy UC Regents Fall 2009 UCB 2 This is how electric tea pots work Heats 1 gram of water 0 24 degree C 0 24 Calories per Second 1A 1V 1 Joule of Heat Energy per Second tt a 1W 1 Ohm Resistor 20 W rating Maximum power the package is able to transfer to the air Exceed rating and resistor burns CS 250 L5 Power and Energy UC Regents Fall 2009 UCB 3 Cooling an iPod nano Like resistor on last slide iPod relies on passive transfer of heat from case to the air Why Users don t want fans in their pocket To stay cool to the touch via passive cooling power budget of 5 W If iPod nano used 5W all the time its battery would last 15 minutes CS 250 L5 Power and Energy UC Regents Fall 2009 UCB 4 Powering an iPod nano 2005 edition Battery has 1 2 W hour rating Can supply 1 2 W of power for 1 hour 1 2 W 5 W 15 minutes More W hours require bigger battery and thus bigger form factor it wouldn t be nano anymore Real specs for iPod nano 14 hours for music 4 hours for slide shows 85 mW for music 300 mW for slides CS 250 L5 Power and Energy UC Regents Fall 2009 UCB 5 Notebooks now most of the PC market 2006 Apple MacBook 5 2 lbs 8 9 in 1 in 12 8 in Performance Must be close enough to desktop performance most people no longer use a desktop Size and Weight Ideal paper notebook Heat No longer laptops top may get warm bottom hot Quiet fans OK CS 250 L5 Power and Energy UC Regents Fall 2009 UCB 6 Battery Set by size and weight limits Battery rating 55 W hour 46x more energy than iPod nano battery And iPod lets you listen to music for 14 hours Almost full 1 inch depth Width and height set by available space weight CS 250 L5 Power and Energy At 2 3 GHz Intel Core Duo CPU consumes 31 W running a heavy load under 2 hours battery life And just for CPU At 1 GHz CPU consumes 13 Watts Energy saver option uses this mode UC Regents Fall 2009 UCB 7 r Pie The IBM Thinkpad CPU is only R40 part of power budget 2004 era notebook T J Watson Research Center running a full workload Current Generation Laptop Power Pie 15 15 4 4 29 4 5 1 other GPU Idle Power 8 1 13 IBM Thinkpad R40 3 CPU 1 LCD Backlight CPU Power Supply LCDLCD Optical Drive Graphics 4 1 3 3 8 26 15 Amdahl s 4 Law for Power 4 1 took no power If our CPU 52 52 at all to13 run that would only double4 battery life HDD Wireless LCD Backlight Memory Rest of the system 1 3 3 Max Power Workload Data courtesy Mahesri et al U of Illinois 2004 CS 250 L5 Power and Energy Max Power Workload 6 Pradip Bose Hot Chips 2005 Tutorial UC Regents Fall 2009 UCB 8 August 14 2005 2004 2005 IBM Corporation ack Stats Servers Total Cost of Ownership TCO Machine rooms are expensive Removing heat dictates how many ser vers to put in a machine room Reliability running computers hot makes them fail more often CS 250 L5 Power and Energy Electric bill adds up Powering the ser vers powering the air conditioners is a big part of TCO UC Regents Fall 2009 UCB 9 Processors and Energy CS 250 L5 Power and Energy UC Regents Fall 2009 UCB 10 Switching Energy Fundamental Physics 0 Every logic transition dissipates energy 1 2 0 03 Vdd Vdd C E0 1 1 2 1 CV dd 2 E1 0 2 1 CV dd 2 4546 3 Strong result Independent of technology How can we limit switching energy 1 Slow down clock fewer transitions But we like speed 2 Reduce Vdd But lowering Vdd limits the clock speed 3 Fewer circuits But more transistors can do more work 4 Reduce C per node One reason why we scale processes CS 250 L5 Power and Energy UC Regents Fall 2009 UCB 012 34 5 67 1 11 Scaling Fundamental Cost per Driver ScalingThe switching energy gate IC process scaling Moore s Law Process Advances Still Scale Power 350nm 200mm 250nm 200mm CV2 Scaling Twice the circuitry in the same space architectural innovation 180nm 200mm OR 130nm 200mm The same circuitry in half the space cost reduction 90nm 300mm 65nm 300mm Dual Core Half the die size for the same capability than in the prior process 32nm 45nm 65nm 90nm 13 m 18 m 25 m 35 m 6 Due to reducing V and C length and width of Cs decrease but plate distance gets smaller Recent slope more shallow because V is being scaled less aggressively From Facing the Hot Chips Challenge Again Bill Holt Intel presented at Hot Chips 17 2005 but the rate has slowed and collaboration is required CS 250 L5 Power and Energy UC Regents Fall 2009 UCB 16 12 hip design Second Factor Leakage Currents Even when Leakage a logic gate isn tPower switching it burns power Static Leakage becomes Significant Isub Even when this nFet akage becomes Significant is off it passes an Ioff current Power scaling vs process for the last 10 years leakage includes frequency increasing with process speed 1 2 VIN 0V VOUT Vdd results in a lower Ion and thus a lower maximum clock speed Leakage 0 8 0 6 Strained silicon reduction Current A 0 4 Di Dt Vdd Gnd Bounce Intel s 2006 processor designs Dynamic Igate Ideal capacitors have 0 2 zero DC current But modern 20 cycles transistor gates are a few 0 35 m 25 m atoms thick and 18 m are not 13 m ideal 90nm oltage V Normalized Product Power wer scaling vs process for the last 10 years We can engineer any Ioff ISub 1 des frequency increasing with process speed CL we like but a lower Ioff also IGate leakage vs switching power Leakage Dynamic 65nm Bill Holt Intel Hot Chips 17 CS 250 L5 Power and Energy 17 Strained silicon reduction A lot of work was done to get a ratio this good 50 50 not unheard of UC Regents Fall 2009 UCB 13 Engineering On Current at 25 nm We can increase Ion by raising Vdd and or lowering Vt Vd Vg Ids Ids Vs 1 2 mA Ion 0 25 Vt Ioff 0 0 7 Vdd CS 250 L5 Power and Energy UC Regents Fall 2009 UCB 14 Plot on a Log Scale to See Off Current Vd Vg Ids Vs We can …