Computing Components

1
Chapter 5

• Computing Components

Nell Dale John Lewis
2
Chapter Goals

• Read an ad for a computer and understand the
  jargon
• List the components and their function in a von
  Neumann machine
• Describe the fetch-decode-execute cycle of the
  von Neumann machine
• Describe how computer memory is organized and
  accessed
• Name and describe different auxiliary storage
  devices
• Define 3 alternative parallel computer
  configurations

3
Computer Components

• Consider the following ad

4
Sizes in Perspective
5
Stored-Program Concept
Figure 5.1 The von Neumann architecture
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Input/Output Units (Peripherals)

• 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

7
Memory

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

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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 (on-chip memory)

9
Control Unit

• Control unit is the organizing force (traffic
  director) 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 together called the
  Central Processing Unit, or CPU

10
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
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Buses

• System bus CPU to main memory
• Expansion bus CPU to peripherals
• EISA bus
• PCI bus
• AGP bus
• USB bus

12
The Fetch-Execute Cycle

• The instruction cycle involves the following
• Fetch the next instruction from RAM into CPU
• Decode the instruction
• Get data if needed
• Execute the instruction

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The Fetch-Execute Cycle
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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

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Hierarchy of Memory

• The hierarchy of memory is classified by the
  speed and the cost of memory
• Level 1 cache (8 - 64 KB) registers in CPU
• Level 2 cache (64 KB 2 MB) SRAM
• RAM (128 MB - 256 MB) DRAM
• Hard disk (40 GB 200 GB) or CD-ROM

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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

17
Magnetic Tape

• The first truly mass auxiliary storage device was
  the magnetic tape drive

Figure 5.4 A magnetic tape
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Magnetic Disks

• A read/write head travels across a spinning
  magnetic disk, retrieving or recording data

Figure 5.5 The organization of a magnetic disk
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Compact Disks

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

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Storage Capacity

• Hard disk 10 G a few 100 G
• DVD 4.7 G 17 G
• CD 650 M 1 G
• Flash drive 256 M 1 G
• Zip disk 100 M 750 M
• Floppy disk 1.44 M

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Parallelism

• Parallel architectures rely on a set of
  interconnected CPUs to offer several ways to
  increase the speed of execution.
• SIMD single-instruction, multiple-data-stream
• Pipelining Multiple processors arranged in
  tandem, where each contributes one part of an
  overall computation
• MIMD multiple-instruction, multiple-data-stream

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Synchronous processing

• One approach to parallelism is to have multiple
  processors apply the same program to multiple
  data sets - SIMD

Figure 5.6 Processors in a synchronous computing
environment
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Pipelining

• Arranges processors in tandem, where each
  processor contributes one part to an overall
  computation

Figure 5.7 Processors in a pipeline
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Shared Memory Configuration

• Different processors do different things with
  different data. The approach allows processors to
  work independently on pieces of the problem and
  yet work together toward the solution of the
  overall problem through coordination among
  processors - MIMD

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Homework

• What are the parts of a CPU? What are their
  functions?
• How do primary storage differ from secondary
  storage? What are the different types of primary
  storage? How do they differ?
• What is an instruction cycle? Give the detail
  steps of the execution of one instruction.
• The computer activities are controlled by
  internal electronic clock. What is the
  relationship between a clock cycle (MHz) and
  execution speed (MIPS)?
• What does a computer bus do? Distinguish between
  system bus and expansion bus.