1Computer Systems are Different!6.033 Spring 2007Static discipline• Be tolerant of inputs and strict on outputsMoore’s law“Cramming More Components Onto Integrated Circuits”, Electronics, April 1965QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.Moore’s Law: # transistors/die doubles every ~18 monthsLithography:the driver behind transistor count• Number of components scales O(n2) with feature size• Switching time scales O(n) with features size• Number of components scale O(n2) with die areaRAM density2CPU performanceDisk: Price per GByte drops at ~30-35% per year1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 200501101001000100001000001000000Dollars per GBMagnetic Disk Price History and ProjectionENIAC• 1stbuilt in 1946• 80 feet• 20 10-digit registers• 18,000 vacuum tubes• 124,500 wattsUNIVAC (Universal Automatic Computer)• Introduced in 1951• 46 delivered in all, until 1958• Predicted ’52 election results based on early results (1%)• 1,905 ops/sec, at 2.25 Mhz clock• 1,000 words of 12 characters• No monitor, only typewriterIBM Systems/360• 1960s• Model 40• 1.6 Mhz• 32-64 Kilobyte• $225,000QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.DEC PDP• PDP-8, 1964• 330,000 adds/s• $16-20K• UNIX introduced on PDP-10QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.3Cray 1: supercomputer• 1976• Most expensive, fastest, best price/performance ratio• $5-8 Million• 166 Million adds/s• 32 MbyteQuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.Apple II• 1977• 6502 microprocessor• 4 to 48 KilobyteQuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.IBM’s wrist watch• 2001• Linux and X11• 19Mhz ARM• 8 Megabyte flash• 8 Megabyte DRAMQuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.Software system complexityMillions of lines of source code0102030405060NASAspaceshuttlectrlWindows3.1(1992)WindowsNT(1992)Solaris(1998)Windows95Windows98WindowsNT 5.0(1998)RedHatLinux 6.2(2000)RedHatLinux 7.1(2001)WindowsXPVistaComputing is everywhere!0100200300400500600700PCs TVs Cars CellphonesMillionsProjected to be 1B in 2005!Internet hosts (names) with time:~40% per year4People-to-computer ratio with timeyearlog (people per computer)streaming informationto/from physical worldNumber CrunchingData Storage productivityinteractiveSlide from David Culler, UC BerkeleyLatency improves slowly11010010001 2 3 4 5 6 7 8 9 10 11Year #Improvement wrt year #1Moore’s law (~70% per year)DRAM access latency (~7% per year)Speed of light(0% per year)Incommensurate doubling Fabrication is expensiveHeat is a problem Itanium Temperature PlotExecution core120oCCache70°CInteger & FP ALUsTemp(oC)[ Source: Intel ]5Principles Adopt sweeping simplifications Avoid excessive generality• Be explicit• Decouple modules with indirection Design for iteration• End-to-end argument Incommensurate scaling rule Law of diminishing returns• Open design principle• Principle of least surprise Robustness principle Unyielding foundations
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