cs2100-19-IO

cs2100-19-IO - CS2100Computer Organisation Input/Output...

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CS2100 Computer  Organisation http://www.comp.nus.edu.sg/~cs2100/ Input/Output (AY2009/2010) Semester 2 Adapted from David Patternson’s lecture slides: http://www-inst.eecs.berkeley.edu/~cs152/
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CS2100 Input/Output 2 THE BIG PICTURE Control Datapath Memory Processor Input Output Control Datapath Memory Processor Input Output Network
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CS2100 Input/Output 3 INPUT/OUTPUT DEVICES
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CS2100 Input/Output 4 WHY I/O MATTERS? CPU performance increase ~ 60% per year I/O performance increase < 10% per year Limited by mechanical delays Amdahl’s Law: system speedup is limited by the slowest part Example: Suppose 1 sec I/O + 4 sec CPU => 5 seconds Increase CPU performance by 100% => 3 seconds We only get 66% speedup => I/O bottleneck “I think Silicon Valley was misnamed. If you look back at the dollars shipped in  products in the last decade, there has been more revenue from magnetic disks than  from silicon. They ought to rename the place Iron Oxide Valley.”  -- Al Hoagland, one  of the pioneers of magnetic disks, 1982
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CS2100 Input/Output 5 TYPES AND CHARACTERISTICS OF  I/O DEVICES Behavior Input: read once Output: write only, cannot be read Storage: can be reread and usually rewritten Partner What’s on the other end? Human or machine Data Rate Peek rate of transfer between I/O and memory/CPU
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CS2100 Input/Output 6 I/O DEVICE EXAMPLES Device Behavior Partner Data Rate (BB/ sec) Keyboard Input Human 0.01 Mouse Input Human 0.02 Line Printer Output Human 1.00 Floppy disk Storage Machine 50.00 Laser Printer Output Human 100.00 Optical Disk Storage Machine 500.00 Magnetic Disk Storage Machine 5,000.00 Network-LAN Input or output Machine 20 – 1,000.00 Graphics Display Output Human 30,000.00
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CS2100 Input/Output 7 MOUSE Invented by Douglas C. Engelbart (jointly with Bill English) in 1970 “SRI patented the mouse, but they really had no idea of its value. Some years later I learned that they had licensed it to Apple for something like $40,000.” -- Douglas C. Engelbart Douglas was as a pioneer of human-computer interaction whose team developed hypertext, networked computers, and precursors to GUIs Mouse uses optimal or mechanical means to determine the X-Y coordinates Bandwidth requirement limited by human hand coordination We are too slow relative to the rate of reading mouse status First computer mouse
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CS2100 Input/Output 8 MAGNETIC DISK Purpose: Long term, nonvolatile storage Large, inexpensive, and slow Lowest level in the memory hierarchy Basic Idea: Rely on a rotating platter coated with a magnetic surface Use a moveable read/write head to access the disk Registers Cache Memory Disk
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CS2100 Input/Output 9 MAGNETIC DISK HISTORY Al Hoagland stands with the RAMAC
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cs2100-19-IO - CS2100Computer Organisation Input/Output...

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