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Session 2:

Session 2:. Computing Components. Nell Dale • John Lewis. Session Goals. Begin to understand the jargon used in computing List the components and their function in a von Neumann machine Describe the fetch-decode-execute cycle of the von Neumann machine. Session Goals (cont.).

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Session 2:

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  1. Session 2: Computing Components Nell Dale • John Lewis

  2. Session Goals • Begin to understand the jargon used in computing • List the components and their function in a von Neumann machine • Describe the fetch-decode-execute cycle of the von Neumann machine

  3. Session Goals (cont.) • Describe how computer memory is organized and accessed • Name and describe different auxiliary storage devices • Define parallel computer configurations

  4. Computing as a Tool Programmer / User Systems Programmer (builds tools) Applications Programmer (uses tools) Domain-Specific Programs User with No Computer Background 20

  5. Computing as a Discipline • Four Necessary Skills • Algorithmic Thinking • Representation • Programming • Design 21

  6. Computer Components • Consider the following ad

  7. Sizes in Perspective • Admiral Grace Murray Hopper • A coil of wire nearly 1,000 feet long • Distance traveled by an electron along the wire in the space of a microsecond • A short piece of wire • In the space of a nanosecond • A bag containing grains of pepper • In the space of a picosecond

  8. Sizes in Perspective

  9. Stored-Program Concept Figure 5.1 The von Neumann architecture

  10. System Components • Hardware • I/O devices (input/output) • keyboard, mouse, monitor, etc. • CPU • Primary Storage • Secondary Storage • Software

  11. Typical System • Computer case • Monitor • Printer • Speakers • Modem • Keyboard • Mouse

  12. Computer Components • Power supply • Hard drive • Expansion card • Expansion slot • System board • CD-ROM or DVD-ROM • Floppy disk • Drive bay • Central Processing Unit (CPU) • Random access memory (RAM)

  13. Processing

  14. The Fetch-Execute Cycle • Fetch the next instruction • Decode the instruction • Get data if needed • Execute the instruction

  15. The Fetch-Execute Cycle

  16. Sample Processing Sequence • Two numbers in main memory are added • Instruction is transferred from memory into the CPU • Location of the instruction being processed is updated in the instruction counter(IC) or program counter (PC) • The instruction just fetched is stored in the instruction register (IR) • CU decodes the instruction to add two numbers • operator [operand1], [operand2], [operand3] • ADDW3 first_no, second_no, answer • W = words, 3 = no of operands in the instruction • Numbers are located in main memory • Fetched into internal registers of the ALU by the CU • Addition is carried out by ALU • Sum stored in new memory location by CU • The IC is updated to point to the next instruction

  17. Memory • Memory is a collection of cells, each with a unique physical address

  18. Computer Architecture • Microprocessor (examples Pentium, Pentium II, PowerPC, etc.) • includes Bus Interface Unit, Arithmetic & Logic Unit (ALU), Control Unit, registers • motherboard is simply the main circuit board that contains most of these parts • the CPU (central processing unit) is considered to be most of these parts taken as a whole • Bus • connects the microprocessor to the RAM & ROM • addresses for data and instructions are important

  19. CPU (Central Processing Unit) • Processes instructions, performs calculations, and manages the flow of information • Performance: • CPU speed is a major factor in determining how fast a computer operates (faster the speed, faster computer operates) • Measured in gigahertz (GHz) A clock cycle relates to the clock that controls the timing in the microprocessor. • For example, a 1.4GHz (gigahertz) clocked microprocessor generates 1.4 billion clock cycles per second. • Each generation of CPU is more powerful than the one before. It's clock cycles are faster at a given speed

  20. Processing • The Central Processing Unit (CPU) is the main chip in a computer • Processes instructions • Performs calculations • Manages the flow of information

  21. Types of CPUs (Chips) • Intel Pentium Processor • Intel Celeron • Needs of home machines • AMD Athlon Processor • Business and home use • AMD Duron Processor • Home use • VIA Cyrix Processor • Inexpensive CPU

  22. Main Memory / Primary Storage • Speeds up computer by storing data the computer has recently used • Internal Cache: On CPU chip (L1 or primary cache • External Cache: On the system board and consists of Static RAM (SRAM chips) • Sometimes built into chip • RAM – slower main memory • Each time the computer requests data from RAM, the computer places a copy of the data in memory cache • Constantly contains the most recently used data

  23. Storage Devices • Primary storage • RAM (Random Access Memory, or just “memory” for short) • active data that is being stored, lost if power is cut off so save often • ROM (Read-Only Memory) • commands that are permanently stored on chips • PC’s use BIOS, Macs use the Toolbox • Secondary storage • Hard disk, floppy disks • Slower method of storage & retrieval but “safer”

  24. Random Access Memory • Random Access Memory – Temporarily stores data inside a computer • Constantly overwritten • Measured in megabytes (MB) • If you have limited memory or you have many programs open, your computer may need to use part of the hard drive to simulate more memory

  25. RAM and ROM • RAM stands for Random Access Memory • Inherent in the idea of being able to access each location is the ability to change the contents of each location • ROM stands for Read Only Memory • The contents in locations in ROM cannot be changed • RAM is volatile, ROM is not • This means that RAM does not retain its bit configuration when the power is turned off, but ROM does

  26. Using Memory • Look through documents on your desk (internal cache) • Look through documents in your desk drawer (external cache) • Looking through documents in your filing cabinet (RAM) • Go out and get it from the trunk of your car (secondary storage)

  27. Control Unit • Control unit is the organizing force in the computer • There are two registers in the control unit • The instruction register (IR) contains the instruction that is being executed • The program counter (PC) contains the address of the next instruction to be executed • ALU and the control unit called the Central Processing Unit, or CPU

  28. Arithmetic/Logic Unit • Performing basic arithmetic operations such as adding • Performing logical operations such as AND, OR, and NOT • Most modern ALUs have a small amount of special storage units called registers

  29. Input/Output Units • An input unit is a device through which data and programs from the outside world are entered into the computer • Keyboard, the mouse, and scanning devices • An output unit is a device through which results stored in the computer memory are made available to the outside world • Printers and video display terminals

  30. Math Coprocessors • A special processing unit that assists the CPU in performing certain operations. • A math coprocessor is a chip or part of a chip that specializes in doing math. Hardware that attaches to the motherboard or is part of the CPU. • Also called numeric coprocessors or floating point units (FPU).

  31. Flow of Information • The parts are connected to one another by a collection of wires called a bus Figure 5.2 Data flow through a von Neumann architecture

  32. Bus • Electronic pathway that carries information between devices in a computer • Bus Width (think lanes of a highway) • 8 bits is one character • Bus Speed (think speed limit) • Measured in MHz (millions of cycles per second)

  33. Parallel Processing

  34. Synchronous processing • One approach to parallelism is to have multiple processors apply the same program to multiple data sets Figure 5.6 Processors in a synchronous computing environment

  35. Pipelining • Arranges processors in tandem, where each processor contributes one part to an overall computation Figure 5.7 Processors in a pipeline

  36. Peripherals

  37. Ports • Ports are connectors at the back of a computer system that you use to plug in an external device. This allow instructions and data to flow between the computer and the device

  38. Any Port in a Storm • Parallel port – 25 holes; female connector; LPT1; printer or storage devices • Monitor port • Keyboard port • Serial port – 9 or 25 pins; male connector; COM1; mouse or modem • Game port • Network port • USB port • 127 devices • Printer, modem, joy stick • Firewire

  39. USB and Firewire • High-speed ports that allow information to quickly transfer between a computer and an external device • USB • Supports up to 127 device • USB 1.0: 12 megabits per second • USB 2.0: 480 Mbps • FIREWIRE • 63 devices at 400 Mbps • Can purchase Firewire expansion card

  40. Storage Devices

  41. Secondary Storage Devices • Because most of main memory is volatile and limited, it is essential that there be other types of storage devices where programs and data can be stored when they are no longer being processed • Secondary storage devices can be installed within the computer box at the factory or added later as needed

  42. Magnetic Disks • A read/write head travels across a spinning magnetic disk, retrieving or recording data Figure 5.5The organization of a magnetic disk

  43. Hard Drives • Magnetically stores data on rotating disks called platters • Capacity is measured in bytes • Speed is measured in revolutions per minute

  44. Floppy Drives and Drives • Removable media • Can be write-protected • Can be damaged magnetically

  45. Magnetic Tape • The first truly mass auxiliary storage device was the magnetic tape drive Figure 5.4 A magnetic tape

  46. Tape Drive • Backup helps you copy files to tape cartridges • Try to find a drive that can store the entire contents of your hard drive

  47. Removable Storage Devices • Jazz Drive – 2 GB • Zip Drive – 250 MB • LS-120 Drive – 120 MB

  48. Compact Disks • A CD drive uses a laser to read information stored optically on a plastic disk • CD-ROM is Read-Only Memory • DVD stands for Digital Versatile Disk

  49. CD-ROM • ROM (Read-only memory) - can’t be changed • 650 Mb of data • Equal to entire set of encyclopedias • 400 Floppy disks • Speed determines how fast a disk spins • Look for 48X • Speed of CD-ROM drive is the transfer rate • In Kb (e.g. 3600Kbs)

  50. CD-R & CD-RW Drives • CD-R (Compact Disc – Recordable) • Permanent store; not erasable • CD-RW • Can be erased and rewritten • Read / Write and Re-write speeds • Usually 74 minutes • Special software needed to record onto a disk • Referred to as burning a CD

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