CS162 03 18 2009 Wed Zhiyi Li Lecture Notes I O Devices Terminal 1 One character is sent at a time one interrupt per character 2 Keyboard and display independent in most systems Full Duples Half Duples Line Printer 1 Fixed 132 character records 2 Control function first character of each line 3 High speed 2000lines per min 4 Print chain Raster Printer a laser or ink jet printer 1 Pixles 300 1200 pixels per liner inch 8 million pixels per page 2 Lasers and xerographic printer 3 Ink jet printer heat or pressure on the cartridge generates ink drop 4 Problem in printer tech nology paper jam Displays 1 CRT Phosphor coated screen Electron beam is created by high voltage Different pixels of each color different color 2 Liquid Crystal LCD pixel liquid crystal passive matrix to select a pixel by column and row backlight light typical LCD power consumption 2 5W 3 Organic Light Emitting Diodes OLED Current induces light emission Efficient no viewing angle limit 4 Plasma Vs LCD cheaper better motion pictures however short lifetime more power consumption 5 Touch Screen don t require much precision Reel to Reel Tape 9 tracks wide by 2400 feet long Disadvantage not addressable read write only in one direction 800 1600 or 6250 bytes per inch dpi Newer IBM Cartridges 3MB sec Expensive DEC Tape Advantages random reads and writes Addressable Disadvantage slow DLT Tape Linear tape system Speed 36MB sec 300GB big Lifetime 30 years Errors 1 bit in 10 17 correctable errors 1 bit in 10 27 permanent errors Tape Summary Incompatible formats Cheap to store data vs slow speed Hard Disck Patters 2 surfaces each top and bottom Cylinder Tracks Sectors Old drives used to use absolute positioning to find a track Today with drives containing over 10k cylinders heads use feedback to find the tracks As they move toward the desired track they read the track info as they go to determinehow much further it needs to move until it actually finds the track Unlike floppies drive heads float over the platter like a glider The spinning platter generate a vortex and the head rides on this vortex of air This gap is generally in the order of micrometers If the drive is jolted the head may crash into the platter and may result in the loss of data
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