The science that drives modern computers.Changing face of manufacturing20th century science and IT: a match made in heaven?PowerPoint PresentationWhy lasers are so useful: Accurate focusingSilicon Chip manufacturingSlide 7Moore’s LawImplementation of a gate in a modern chipExample: an AND gateChip FabricationAside: Lasik eye correctionChip PackagingLife cycle of a microprocessorWhy so few new CPU’s?Engineering tradeoffsEven more precise control of matterAnother example of control of matter: the changing data cableTotal Internal ReflectionHow optical fibers workWave Division Multiplexing (WDM)Thoughts about the 20th centuryAre faster chips the answer to all problems in computing?What about this decidable problem?Next time: Computer Viruses, Worms, and ZombiesThe science that drives modern computers.COS 116: 4/8/2008Sanjeev AroraChanging face of manufacturing1936 Late 20th century “Modern Times”Silicon wafer fabrication20th century science and IT: a match made in heaven?“These are the days of miracles and wonders.” – Paul Simon, GracelandMain theme in this lecture: Scientific Advances Ability to control matter precisely Amazing products/computersQuantum mechanics (wave-particle duality, quantization of energy, etc.)Ability to create light of a single frequency (“laser”)Example of precise control of matter: LasersWhy lasers are so useful: Accurate focusingWhite lightDifferent colors focus at different points – “smudge”LaserFocus at single pointSilicon Chip manufacturing “A picture is worth a billion gates.”Fact: Modern chips are manufactured using a process similar to photographyTimelineVacuum Tube Triode (1908)Transistor1947(silicon, germanium)Very Large ScaleIntegrated (VLSI)Circuits; 1970s--(> 1,000 transistorsper chip)Intel Itanium (Tukwila) 2008: 2 billion transistorsMoore’s Law Technology advances so that number of gates per square inch doubles every 18 months.[Gordon Moore 1965]Number of gates doubling every 24 monthsNumber of gates doubling every 18 monthsImplementation of a gate in a modern chipSemiconductor: not as good a conductor as metals, not as bad as woodExample: siliconDoped semiconductor: semiconductor with some (controlled) impurities: p-type, n-typeSwitch: p-n junctionExample: an AND gateNNPABPowerOutputGroundNNPChip FabricationGrow silicon ingotsCut wafers and polishCreate maskCoat with chemicals that remove parts unexposed to light Repeat to add metal channels (wires) and insulation; many layers! Coat wafer with light sensitive chemicals and project mask onto itAside: Lasik eye correctionUses laser invented for chip fabricationChip PackagingInsideOutsideLife cycle of a microprocessorFact: Less than 1% of microprocessors sold are used in computersInside an iPod RemoteWhy so few new CPU’s?Cost of new design: $8 billionProfit: $100 / chipNeed to sell 80 million to break evenCost of new design: $8 billionProfit: $100 / chipNeed to sell 80 million to break evenEngineering tradeoffs36 months later...Can run at twice the clock speed! (Why?)But: higher clock speeds much more heat!Half the size!Even more precise control of matterNanotechnology: manufacture of objects (machines, robots, etc.)at the atomic or molecular level (1-100 nanometers)“nanogear”Biocomputing: Implementing computers via interactions ofbiological molecules.Another example of control of matter: the changing data cableSerial cable: 115 kb/sUSB cable: 480 Mb/s (USB 2.0)Fiber optic cable: 40 Gb/sTotal Internal ReflectionPorro PrismHow optical fibers workGlass fiber: 10-40 billion bits/s “Total internal reflection”PulsingLaser beamTransmission rates of trillion (“Tera”) bits/sWave Division Multiplexing (WDM)MultiplexorDe-multiplexorMultiple (100 or so) data streams enterOne beam with various frequencies mixed inMultiple data streams exitFiber optic cableThoughts about the 20th centuryWhat factors (historical, political, social) gave rise to this knowledge explosion? Will it continue in the future?As we know,There are known knowns.There are things we know we know.We also knowThere are known unknowns.That is to sayWe know there are some thingsWe do not know.But there are also unknown unknowns,The ones we don't knowWe don't know.— D. Rumsfeld, Feb. 12, 2002Are faster chips the answer to all problems in computing?An Answer: No! Halting problem is undecidable!What about this decidable problem?Does it have a satisfying assignment?What if instead we had 100 variables?1000 variables?(A + B + C) · (D + F + G) · (A + G + K) · (B + P + Z) · (C + U + X)Next time:Computer Viruses, Worms, and
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