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Unformatted text preview: Chapter 5: Computing Components
In the 1940s and 1950s, John von Neumann helped develop the architecture that continues to be used in the design of most modern computer systems. Control Unit, Coordinati ng CPU Activity Arithmetic/ Logic Unit, Processin g Data Chapter 5 Computing Components Page 1 Central Processing Unit (CPU)
Storage for instructions for deciphering data Branch Predictor Unit
Decides which ALU can best handle specific data & divides the tasks Bus Interface Unit
Information from the RAM enters the CPU here , and then it is sent to separate storage units or cache Instruction Prefetch & Decoding Unit
Translates data into simple instructions for ALU to process Arithmetic Logic Unit
Whole number cruncher Floating Point Unit
Floating-point number cruncher Data Cache
Sends data from ALUs to Bus Interface Unit, and then back to RAM Instruction Register
Provides the ALUs with processing instructions from the data cache
Chapter 5 Computing Components Page 2 Simplified View of the CPU CPU
Circuitry that manipulates the data Register s
Special memory cells to temporarily store the data being manipulated Control Unit
Circuitry to coordinate the operation of the computer Bus RAM Chapter 5 Computing Components Page 3 The Processing Cycle
DECODE instruction to determine what to do ARITHMETIC/LOGIC UNIT
EXECUTE the decoded instruction FETCH the next instruction from main memory STORE the result in main memory MAIN MEMORY
Chapter 5 Computing Components Page 4 Sample Machine Architecture
0 1 2 3 4 5 6 7 8 9 A B C D E F Main Memory Cells Control Unit
(Keeps track of the address of the next instruction to be executed) Bus ALU Instruction Register
(Contains a copy of the 2-byte instruction currently being executed) 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 : : : EE EF F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 FA FB FC FD FE FF : Chapter 5 Computing Components Page 5 Random Access Memory (RAM) Whenever a computer accesses information (e.g., a program that's being executed, data that's being examined), that information is stored as electronic pulses within main memory. Main memory is a system of electronic circuits known as random access memory (RAM), the idea being that the user can randomly access any part of memory (as long as the location of what's being accessed is known). The circuitry in main memory is usually dynamic RAM, meaning that the binary values must be continuously refreshed (thousands of times per second) or the charge Chapter 5 Computing Components Page 6 Cache Memory Due to the need for continuous refreshing, dynamic RAM is rather slow. An alternative approach is static RAM, which uses "flip-flop" circuitry that doesn't waste time refreshing the stored binary values. Static RAM is much faster than dynamic RAM, but is much more expensive. Consequently, it is used less in most machines. Cache memory uses static RAM as the first place to look for information and as the place to store the information that was most recently accessed (e.g., the current program being executed).
Chapter 5 Computing Components Page 7 Magnetic Memory When the power is turned off, a computer's electronic memory devices immediately lose their data. In order to store information on a computer when it's turned off, some non-magnetic storage capability is required. Most computers contain hard drives, a system of magnetic platters and read-write heads that detect the polarity of the magnetic filaments beneath them (i.e., "reading" the bit values) and induce a magnetic field onto the filaments (i.e., "writing" the bit values).
Chapter 5 Computing Components Page 8 Disk Tracks and Sectors Each platter is divided into concentric circles, called tracks, and each track is divided into wedges, called sectors. The read-write head moves radially towards and away from the center of the platter until it reaches the right track. The disk spins around until the read-write head reaches the appropriate sector. Chapter 5 Computing Components Page 9 Floppy Disks Portable magnetic memory devices, known as floppy disks, have limited storage capacity, slow revolution speeds, and long access times, but they are easily removed from a machine and installed in another computer. Chapter 5 Computing Components Page 10 Optical Memory Compact Disks Read-Only Memory (CD-ROMs) use pitted disks and lasers to store binary information. When the laser hits an unpitted "land", light is reflected to a sensor and interpreted as a 1-bit; when the laser hits a pit, light isn't reflected back, so it's interpreted as a 0-bit. Digital Versatile Disks (DVDs) use the same pits-andlands approach as CD-ROMs, but with finer gaps between tracks and pits, resulting in over four times the storage capacity as CD-ROMs. Chapter 5 Computing Components Page 11 Flash Memory Recent advances in memory circuitry have made it possible to develop portable electronic devices with large memory capacities. Flash memory is Electrically Erasable Programmable Read-Only Memory (EEPROM): Read-Only Memory: Nonvolatile (retains data even after power is shut off), but difficult to alter. Programmable: Programs aren't added until after the device is manufactured, by "blowing" all fuses for which a 1-value is desired. Electrically Erasable: Erasing Universal Serial Bus (USB) Connector to Host Computer USB Mass Storage Controller Flash Test Memory Points Chip for LEDs to Crystal Verifying Indicate Oscillator Proper Data to Produce Loading Transfers Clock Signal WriteProtect Switch Space for Second Flash Memory Chip Chapter 5 Computing Components Page 12 Input Device: Keyboard
One of the principal devices for providing input to a computer is the keyboard. When a key is pressed, a plunger on the bottom of the key pushes down against a rubber dome... ...the center of which completes a circuit within the keyboard, resulting in the CPU being signaled regarding which key (or keys) has been pressed. Chapter 5 Computing Components Page 13 Input Device: Mouse
The other primary input device is the computer mouse. Optical Mouse Mechanical Mouse
The mouse driver software processes the X and Y data and transfers it to the operating system Moving the mouse turns the ball X and Y rollers grip the ball and transfer movement Optical encoding disks include light Sensors holes gather light pulses to convert to X and Y velocities Infrared LEDs shine through the disks Optical mice use red LEDs (or lasers) to illuminate the surface beneath the mouse, and sensors detect the subtle changes that indicate how much and in what direction the mouse is being moved.
Chapter 5 Computing Components Page 14 Output Device: Cathode Ray Tube (CRT)
Deflection Coils These magnetic plates deflect the beams horizontally and vertically to particular screen coordinates Anode Connection The positive charge on the anode attracts the electrons and accelerates them forwards Focusing Coil The magnetic coil forces the electron flows to focus into tight beams Electron Guns A heating filament releases electrons from a cathode, which flow through a control grid (controlling brightness) Shadow Mask A perforated metal sheet halts stray electrons and ensures that beams focus upon target phosphors Phosphor-Coated Screen Each pixel is comprised of a triad of RGB phosphors that are illuminated by the three electron beams Chapter 5 Computing Components Page 15 Output Device: Liquid Crystal Display
Twisted Nematic Liquid Crystals Twists shaft of light 90 when uncharged, 0 when fully charged Color Filter Provides red, green, or blue color to resulting light Light Source Horizontal Polarizer Converts light into horizontal shafts Thin Film Transistor Applies charge to individual subpixel Vertical Polarizer Amount of light permitted to pass is proportional to how close to vertical its shafts are Chapter 5 Computing Components Page 16 Output Device: Plasma Display
Dielectric Layer Contains transparent display electrodes, arranged in long vertical columns Plasma Cells Phosphor coating is excited by plasma ionization and photon release Pixel Comprised of three plasma cells, one of each RGB phosphor coating Rear Plate Glass Dielectric Layer Contains transparent address electrodes, arranged in long horizontal rows Front Plate Glass Chapter 5 Computing Components Page 17 Input/Output Device: Touch Screen Resistive
The glass layer has an outer coating of conductive material, and insulating dots separate it from a flexible membrane with an inner conductive coating. When the screen is touched, the two conductive materials meet, producing a locatable voltage. Capacitive
Small amounts of voltage are applied to the four corners of the screen. Touching the screen draws current from each corner, and a controller measures the ratio of the four currents to determine the touch location. Infrared
A small frame is placed around the display, with infrared LEDs and photoreceptors on opposite sides. Touching the screen breaks beams that identify the specific X and Y coordinates. Acoustic
Four ultrasonic devices are placed around the display. When the screen is touched, an acoustic pattern is produced and compared to the patterns corresponding to each screen position.
Chapter 5 Computing Components Page 18 Parallel Processing Traditional computers have a single processor. They execute one instruction at a time and can deal with only one piece of data at a time. These machines are said to have SISD (Single Instruction, Single Data) architectures. When multiple processors are applied within a single computer, parallel processing can take place. There are two basic approaches used in these "supercomputers": SIMD (Single Instruction, Multiple Data) Architectures MIMD (Multiple Instruction, Multiple Data) Architectures Each processor does the same thing At any given moment, each processor does its own task to its own portion of at the same time to its own portion of the data the data Example: Have some processors Example: Have the processors retrieve data, some perform perform the graphics rendering for calculations, and some render the different sectors of the viewscreen: resulting images: Chapter 5 Computing Components Page 19 ...
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This note was uploaded on 08/26/2009 for the course CS 111 taught by Professor Klein,s during the Fall '08 term at Southern Illinois University Edwardsville.
- Fall '08
- Computer Science