Hardware: The CPU

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Hardware The CPU Storage

• Chapter 5
• How to Buy a Multimedia Computer

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Key Questions

• 5.1 What is a CPU? What are the three components
  of a CPU and what are their functions?
• 5.2 What are machine languages and how
  instructions are executed?
• 5.3 How is data represented in a computer what
  are the components of the system cabinet what
  are processing speeds how do the processor and
  memory work and what are some important ports,
  buses, and cards?
• 5.4 What are the features of floppy disks, hard
  disks, optical disks, magnetic tape, smart cards,
  and online secondary storage?

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CPU and Main Memory

• CPU Central Processing Unit
• the brain of the computer
• Control the operating of the computer
• Main Memory
• Hold data being processed
• Hold Program being executed
• Primary Storage
• RAM Random Access Memory

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The CPU and main memory
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Main Memory

• Random Access Memory (RAM)
• Primary storage or memory
• Used to
• Holds data for processing
• Holds instructions for processing data
• Main memory is volatile
• the contents are lost when the power is turned
  off.
• Therefore, the data must be saved to a secondary
  storage device for later use.

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Main Memory - contd

• The more memory, the more powerful
• Hold more programs/data at a time.
• The capacity of memory varies with different
  computers
• bit or binary digit 0/1
• byte (8 bits each) one character
• Kilobyte 1024 bytes 1 thousand
• Megabyte 1024 Kilobytes 1 million
• Gigabyte 1024 Megabytes 1 billion
• Terabyte 1024 Gigabytes 1 trillion
• Each byte has a unique address

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Three Components of a CPU

• The control unit
• Like a symphony director
• Control the rest of the system to carry out
  programs instructions.
• The Arithmetic/logic unit (ALU)
• Perform arithmetic and logical operations
• Registers
• Fastest storage device
• instruction register hold the instruction to be
  executed next
• data registers store data to be processed by ALU
• address registers Hold the addresses of RAM

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System Clock and Word Size

• System clock
• Generate a sequence of digital pulses
• To control how fast the processor executes
• MHz 1 million pulses per second
• The faster the clock, the faster the processor.
• Word Size
• The of bits the CPU can manipulate at a time.
• A 32-bit-word PC is faster than an 8-bit-word PC
  with the same system clock
• The Power of a Processor
• Determined by the system clock and word size.

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Machine Language

• A Language a computer hardware can run directly.
• Programs in BASIC or PASCAL must be translated
  into the machine language before it is executed
  by the hardware.
• An instruction consists of three parts
• operation code add/subtract
• two operands source and destination
• Example add M(10), M(20)
• 01011100 Add
• 00001000 operand 1
• 00010100 operand 2, location of result

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How an Instruction is Processed

• Instructions are stored in memory
• The CPU can only execute instructions that are
  stored in memory, not on 2nd storage.
• Machine Cycle
• a series of operations performed to execute a
  single program instruction
• Instruction cycle
• The control unit fetches the instruction from RAM
  to the instruction register
• It then decodes the instruction
• Execution cycle
• The ALU executes the instruction
• It then stores the result in memory

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The machine cycle
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How Data is Represented

• Binary System Using Two States bits
• Representation of numbers
• Position value
• Decimal
• E.g., 342, it reads three hundred forty two,
• or three hundreds, four tens, and two ones.
• I.e., each position has position value
• So, 3102 4101 2100
• Binary
• E.g., 10111
• The position value of position i is ith power of
  2
• Starting from the rightmost bit as position zero.
• So, 124 023 122 121120
• 16 0 4 2 1
• 23

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How Data is Represented

• Binary System Using Two States bits
• Binary Coding Schemes for symbols/letters
• EBCDIC
• Extended Binary Coded Decimal Interchange code.
• One byte for a character
• Used on mainframe computers
• ASCII
• American Standard Code for Information
  Interchange
• One byte for a character
• Used on microcomputers
• Unicode
• Code foreign characters as well as English.
• Two bytes for a character.
• Used more and more

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Binary data representation of symbols
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Two coding schemes EBCDIC and ASCII-8
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The Microcomputer System Unit

• Power Supply
• Surge protectors
• Prevent damages from power surges
• Uninterruptable power supply (UPS)
• Provide temporary power supply when the main
  power is off so the user can save data to disk.
• Motherboard
• The circuit that connects all the devices
  together.
• CPU Chip
• Intel-type chips
• Motorola-type chips
• 68000-series
• PowerPC

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System unit and motherboard components
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Microcomputers and microprocessors
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The Microcomputer System Unit

• Specialized Processor Chips
• Math coprocessor chip
• Graphics coprocessor chip
• Types of processing
• Serial
• Parallel
• RAM Chips
• Main memory or primary storage
• Inline memory modules (SIMM / DIMM)
• Dynamic RAM (DRAM)
• Static RAM (SRAM)

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The Microcomputer System Unit

• ROM Chips
• Other Forms of Memory
• Cache memory
• Video memory or video RAM
• Expansion Slots Boards
• Expanded memory
• Display adapter or graphics adapter
• Controller cards

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The Microcomputer System Unit

• Bus Lines
• Expansion bus
• Local bus
• Ports
• Parallel ports
• Serial ports or RS-232 ports
• Video adapter ports
• Small computer system interface (SCSI)

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Buses
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I. Storage Fundamentals

• Units of Measurement for Storage
• Kilobyte/Megabyte/Gigabyte/Terabyte
• Data Access Methods
• Sequential Storage
• magnetic tapes
• Direct Access Storage
• Hard disks, floppy disks, CD-ROMs

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II.Criteria for Rating Storage Devices

• Storage Capacity
• of bytes the disk can hold
• Access Speed
• the time needed to locate data
• Transfer Rate
• the speed at which data is transferred
• Removability
• the device that can be removed/installed
• Cost

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III. Diskettes

• The Disk Drive1. Read2. Write
• How A Disk Drive works
• Magnetic coating on the disk
• Read/Write head (R/W head)
• While disk spins, R/W head can read/write

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Cutaway view of a disk drive
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Diskettes

• C. Characteristics of Diskettes
• Tracks and Sectors
• track a circular band on the surface
• Sector a segment of track
• Unformatted versus formatted disks
• Format define tracks and sectors
• Data capacitysides and densities
• Write-protect features

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Diskette anatomy
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IV. Hard Disks

• Hard-disks
• Multiple diskettes stacked in one pack.
• Each diskettes has its own R/W on both sides
• Hard-disk Connections
• SCSI Small Computer System Interface
• EIDE Enhanced Integrated Drive Electronics
• Fragmentation Defragmentation
• Cluster the unit the computer can access at a
  time from disk, multiple sectors
• Fragmentation a file spread out over many
  noncontiguous sectors

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Microcomputer hard-disk drive
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Multiple disks and cylinders
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V. Optical Disks 

• CD-ROM (Compact Disk - Read Only Memory)
• Data is read/written through laser beams
• Single-speed 1x 150KB/Second, 150kbps
• 16x 2400kbps, 32x 4800kbps
• CD-R Disks Recording Your Own CDs
• Compact diskrecordable
• Compact disk - Recordable and reWriteable
• DVD The Digital Convergence Disk
• New generation of high-density CD-ROM

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Optical disks