UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-Up2011-11-29Elad Alontoday’s lecture by John LazzaroCS 150 Digital DesignLecture 23 – Course Wrap-Upwww-inst.eecs.berkeley.edu/~cs150/TAs: Daiwei Li, James Parker, Dan Yeager1UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-UpEnergy and PerformanceSad fact: Computers turn electrical energy into heat. Computation is a byproduct.Air or water carries heat away, or chip melts.2UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-Up+1V-1 Ohm Resistor1A1 Joule heats 1 gram of water 0.24 degree CThis is how electric tea pots work ...1 Joule of Heat Energy per Second1 Watt20 W rating: Maximum power the package is able to transfer to the air. Exceed rating and resistor burns.The Watt: Unit of power. The amount of energy burned in the resistor in 1 second.The Joule: Unit of energy.Can also be expressed as Wat t-Seconds. Burning 1 Watt for 100 seconds uses 100 Watt-Seconds of energy.3UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-UpCooling 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 ...4UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-UpPowering an iPod nano (2005 edition)1.2 W-hour battery: Can supply 1.2 watts of power for 1 hour.1.2 W / 5 W = 15 minutes.Real specs for iPod nano : 14 hours for music, 4 hours for slide shows.85 mW for music.300 mW for slides.More W-hours require bigger battery and thus bigger “form factor” -- it wouldn’t be “nano” anymore :-).5UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-UpFinding the (2005) iPod nano CPU ...Two 80 MHz CPUs. One CPU used for audio, one for slides.Low-power ARM roughly 1mW per MHz ... variable clock, sleep modes.85 mW system power realistic ...A close relative ...6UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-UpiPod nano 200514 hours batterylife(audio playback)Year-to-year: continuous improvementsSource: ifixit.comiPod nano 200624 hours batterylife(audio playback)What changed inside ?7UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-UpSource: ifixit.com8UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-UpSource: ifixit.com9UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-UpiPod nano 2005 - a C-shaped PC board, with a battery in the “C” opening.iPod nano 2006 -battery lies on top of PC board.Source: ifixit.com10UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-UpHow? Small IC packages, fewer partsiPod nano 2006 iPod nano 2005 Source: arstechnica.com11UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-UpAluminum permits thinner case ...Source: ilounge.comWhat’s happened since 2006?12UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-Up0.74 ouncesSources: iFixit, Apple0.39 W Hr (33% of 2005 Nano)2010 Nano: “up to” 24 hours audio playback2010 Nano2010 Shuffle: “up to” 15 hours audio playback0.44 ounces0.19 W Hr2010 Shufflenearly the same depth13UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-UpDesired screen size sets smartphone W x LDepth? : Thin body vs. Battery life14UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-Up22% gain in battery energy over 5 iterations15UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-UpiPhone (2007)MainboardAntennasBattery16UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-UpiPhone 4{,S}BatteryL-shape Main BoardMetal frame acts as antenna17UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-UpIn 4 years:6.8x increase in transistor count33% max clock speed increaseAttached DRAM: 128 MB -> 512 MB6.8x transistors: Dual CPU and GPU,and to save energy.18UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-UpNotebooks ... as designed in 2006 ...Performance: Must be “close enough” to desktop performance ... most people no longer used a desktop (even in 2006).Heat: No longer “laptops” -- top may get “warm”, bottom “hot”. Quiet fans OK.Size and Weight. Ideal: paper notebook.1 in8.9 in12.8 in2006 Apple MacBook -- 5.2 lbs19UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-UpBattery: Set by size and weight limits ...Almost full 1 inch depth. Width and height set by available space, weight.Battery rating: 55 W-hour.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 ...46x more energy than iPod nano battery. And iPod lets you listen to music for 14 hours!20UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-Up55 W-hour battery stores the energy of 1/2 a stick of dynamite.If battery short-circuits, catastrophe is possible ...21UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-Up22UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-UpMacBook Air ... design the laptop like an iPod23UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-Up2011 Air: 11.8 in x 7.56 in2006 Macbook: 12.8 in x 8.9 in0.11 in0.68 inx 0.68 in; 2.38 lbsx 1 in; 5.2 lbs24UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-UpNon-removable, “form-fit” battery ...Mainboard: fills about 25% of the laptop35 W-h battery: 63% of 2006 MacBook’s 55 W-h25UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-Up26UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-Up2011 Air: 35 W-h battery, 5 hour battery lifeiPad 2: 25 W-h battery, 10 hour battery lifeiPad 2: 1.33 lbsMacBook Air 11.6 in: 2.38 lbsBattery-Life-Hour/W-h: 2.8x iPad advantage*For a content-consumption workload.**27UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-Up2011 Air: $999 -- 64 GB SSD, 2 GB RAM, x86iPad 2: $699 -- 64 GB SSD, 512 MB RAM, ARM“Content Creation vs. Content Consumption”iPhone 4S and iPad 2: Identical CPU/RAM stack28UC Regents Fall 2011 © UCBCS 250 L12: System ContextMacBook Air: Full PCTo pBottomCore i5 CPU/GPUPlatform Controller HubThunderbolt I/O4GB DRAM29UC Regents Fall 2011 © UCBCS 150 L23: Course Wrap-UpThe CPU is only part of power budget!T.J. Watson Research Center© 2004, 2005 IBM Corporation6 Pradip Bose| Hot Chips 2005 Tutorial August 14, 2005Current Generation Laptop Power Pie15%4%5%1%8%26%1%3%8%29%CPU HDDPower Supply WirelessLCD LCD BacklightOptical Drive MemoryGraphics Rest of the system52%3%3%1%4%13%1%4%4%15%Idle PowerMax Power Workload(IBM Thinkpad R40)Data courtesy Mahesri et al., U of Illinois, 20042004-era notebook running a full
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