The architecture of computer hardware and systems software an information technology approach ch10

Chapter 10 Computer Peripherals The Architecture of Computer Hardware and Systems Software: An Information Technology Approach 3rd Edition, Irv Englander John Wiley and Sons  2003 Peripherals  Devices that are separate from the basic computer  Not the CPU, memory, power supply  Classified as input, output, and storage  Connect via  Ports  parallel, USB, serial  Interface to systems bus  SCSI, IDE, PCMCIA Chapter 10 10-2 Storage Devices  Primary memory  Expanded storage  Secondary storage  Data and programs must be copied to primary memory for CPU access  Permanence of data  Direct access storage devices (DASDs)  Online storage  Offline storage – loaded when needed Chapter 10 10-3 Speed  Measured by access time and data transfer rate  Access time: average time it takes a computer to locate data and read it  millisecond = one-thousandth of a second  Data transfer rate: amount of data that moves per second Chapter 10 10-4 Hierarchy of Storage Device Typical Access Times Throughput Rate CPU Registers Cache Memory (SRAM) 15 to 30 nanoseconds Conventional Memory (DRAM) 50 to 100 nanoseconds Expanded Storage (RAM) 75 to 500 nanoseconds Hard Disk Drive Floppy Disk CD-ROM Tape Chapter 10 10 to 50 milliseconds 95 milliseconds 100 to 600 milliseconds and up seconds 600 to 6,000 KB/sec 100 to 200 KB/sec 500 to 4,000 KB/sec 2,000 KB/sec (cartridge) 10-5 Secondary Storage Devices        Hard drives, floppy drives CD-ROM and DVD-ROM drives CD-R, CD-RW, DVD-RAM, DVD-RW Tape drives Network drives Direct access vs Sequential access Rotation vs Linear Chapter 10 10-6 Magnetic Disks      Track – circle Cylinder – same track on all platters Block – small arc of a track Sector – pie-shaped part of a platter Head – reads data off the disk  Head crash  Parked heads  Number of bits on each track is the same! Denser towards the center  CAV – constant angular velocity  Spins the same speed for every track  Hard drives – 3600 rpm – 7200 rpm  Floppy drives – 360 rpm Chapter 10 10-7 A Hard Disk Layout Chapter 10 10-8 Locating a Block of Data  Average seek time: time required to move from one track to another  Latency: time required for disk to rotate to beginning of correct sector  Transfer time: time required to transfer a block of data to the disk controller buffer Chapter 10 10-9 Disk Access Times  Avg Seek time  average time to move from one track to another  Avg Latency time  average time to rotate to the beginning of the sector  Avg Latency time = ½ * 1/rotational speed  Transfer time  1/(# of sectors * rotational speed)  Total Time to access a disk block  Avg seek time + avg latency time + avg transfer time Chapter 10 10-10 Display Screen  Screen size: measured diagonally  Resolution: minimum identifiable pixel size  Aspect ratio: x pixels to y pixels  4:3 on most PCs  16:9 on high definition displays Chapter 10 10-21 Color and Displays  Pixel color is determined by intensity of colors – Red Green Blue or RGB  bits per color  16 x 16 x 16 = 4096 colors  24 bit color (True Color)  16.7 million colors  Video memory requirements are significant! Chapter 10 10-22 CRT’s and Text Monitors  CRTs (similar to TVs)     stripes of phosphors for each color separate electron guns for each color Strength of beam  brightness of color Raster scan   30x per second Interlaced vs non-interlaced (progressive scan)  Text monitors     24 lines x 80 chars A character is the smallest unit on a screen Very little memory required Fast for remote transmissions Chapter 10 10-23 Interlaced vs Noninterlaced Chapter 10 10-24 Diagram of Raster Screen Generation Process Chapter 10 10-25 Display Example Chapter 10 10-26 LCD – Liquid Crystal Display  Fluorescent light panel  color cells per pixel  Operation  1st filter polarizes light in a specific direction  Electric charge rotates molecules in liquid crystal cells proportional to the strength of colors  Color filters only let through red, green, and blue light  Final filter lets through the brightness of light proportional to the polarization twist Chapter 10 10-27 LCD Operation Chapter 10 10-28 LCDs (continued)  Active matrix  One transistor per cell  More expensive  Brighter picture  Passive matrix  One transistor per row or column  Each cell is lit in succession  Display is dimmer since pixels are lit less frequently Chapter 10 10-29 Printers  Dots vs pixels  300-2400 dpi vs 70-100 pixels per inch  Dots are on or off, pixels have intensities  Types       Typewriter / Daisy wheels – obsolete Dot matrix – usually 24 pins, impact printing Inkjet – squirts heated droplets of ink Laserjet Thermal wax transfer Dye Sublimation Chapter 10 10-30 Creating a Gray Scale Chapter 10 10-31 Laser Printer Operation Dots of laser light are beamed onto a drum Drum becomes electrically charged Drum passes through toner which then sticks to the electrically charged places Electrically charged paper is fed toward the drum Toner is transferred from the drum to the paper The fusing system heats and melts the toner onto the paper A corona wire resets the electrical charge on the drum Chapter 10 10-32 Laser Printer Operation Chapter 10 10-33 Laser Printer Operation Chapter 10 10-34 Other Computer Peripherals  Scanners  Flatbed, sheet-fed, hand-held  Light is reflected off the sheet of paper  User Input Devices  Keyboard, mouse, light pens, graphics tablets  Communication Devices  Telephone modems  Network devices Chapter 10 10-35 ... access time and data transfer rate  Access time: average time it takes a computer to locate data and read it  millisecond = one-thousandth of a second  Data transfer rate: amount of data that... removable  Another version includes the disk head and arm assembly in the case  Fixed-head disk drives  One head per track  Eliminates the seek time  Bernoulli Disk Drives  Hybrid approach. .. – small arc of a track Sector – pie-shaped part of a platter Head – reads data off the disk  Head crash  Parked heads  Number of bits on each track is the same! Denser towards the center 