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The Components of the System Unit Chapter 4. Lisa Schulke. What exactly is the System Unit?. A case that contains electronic components used to process data Sometimes called the chassis which protects the internal electronic components

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what exactly is the system unit
What exactly is the System Unit?
  • A case that contains electronic components used to process data
  • Sometimes called the chassis which protects the internal electronic components
    • Includes the Motherboard which is the main circuit board of the system unit
more about the motherboard
More about the Motherboard
  • Many electronic components attach to the board
  • Those components include: adapter cards, the processor, and memory chips
    • A computer chip is a small piece of semi conducting material which have integrated circuits
  • Other components are built into the board
the processor a component
The ProcessorA component
  • central processing unit
  • Interprets & carries out basic instructions that operate a computer
  • Manages the computer’s operations
  • Contain 2 smaller components
    • Control unit
    • Arithmetic logic unit
the control unit the arithmetic logic unit
Directs & coordinates operation

Interprets each instruction issued by a program & initiates the appropriate action to carry out the instruction

Arithmetic operations

Basic calculations

Comparison operations

Comparing 1 data to another

Logical operations

And, or, and Not

The Control Unit The Arithmetic Logic Unit
the machine cycle 4 basic operations of a processor
The Machine Cycle: 4 basic operations of a processor
  • Fetching- obtaining a program instruction or data from the memory
  • Decoding- translating instructions into signals
  • Execute- carries out the commands
  • Storing- writing result to memory
plenty more about processors
Plenty more about processors
  • Contains:
    • A register which is storage location that temporarily holds data and instructions
    • A system clock that control the timing of computer operations
      • Clock speed
names of processors
Names of Processors
  • Pentium- used by high performance PCs
  • Celeron- used by less expensive basic PCs
  • Xeon and Itanium- ideal for workstations and low-end servers
processor installation and upgrades
Processor Installation and Upgrades
  • 3 types of Upgrades
    • Chip-for-chip
    • Piggyback
    • Daughterboard
new chips cause heat
New chips cause heat
  • A heat sink is a small ceramic component that absorbs and ventilates heat produced by electrical components
  • A heat pipe cools processors in notebook computers
coprocessors and parallel processing
A coprocessor is a special chip or circuit board that assists the processor in performing tasks

Floating point has numeric capabilities

Parallel processing is a method that uses multiple processors to execute a program.

Coprocessors and Parallel Processing
data representation
Data Representation
  • Computers communicate digitally and recognize only 2 discrete states: on and off
    • recognizes the 2 states by the binary system which only has 2 unique digits( 0 & 1), called bits
      • 8 bits form a byte
coding scheme
Coding scheme
  • The combinations of 0s and 1s that represent characters are defined by patterns called the coding scheme
    • Example: #3 is represented by 00110101
  • The 2 popular coding schemes:
    • ASCII and EBCDIC
  • Consists of electronic components that store instructions waiting to be executed by the processor, data, and the results of processed data (info)
what memory stores
What memory stores?
  • 3 basic categories of items:
    • The operating system and other system software that control or maintain the computer and its devices
    • The application programs that carry out a specific task, such as word processing
    • The data being processed by the application programs and resulting information
more about memory
More about Memory
  • A byte resides temporarily in a location called the address
    • An address is a unique number that identifies the location of the byte
  • To access data in memory, the computer references the addresses that contain bytes of data
sizes of memory
Sizes of Memory
  • A kilobyte is equal to exactly 1,024 bytes
  • A megabyte is equal to almost 1 million bytes
  • A gigabyte equals almost 1 billion bytes

2 types of Memory

  • Volatile- when the computer’s power is turned off it loses its contents
  • Nonvolatile- does not lose its contents
  • Stands for Random access memory or main memory
  • Consists of memory chips that can be read from and written to by the processor
  • It can hold multiple programs simultaneously
  • Most Ram is volatile
2 basic types of ram chips
Dynamic Ram

Must be re-energized constantly or they lose their contents

Static Ram

Do not have to be re-energized as often

More expensive

Faster and more reliable

2 basic types of ram chips
where do ram chips live
Where do RAM chips live?
  • Usually reside on a memory module which is a small circuit board
    • Memory slots on the motherboard hold memory modules
  • 3 types of modules:
    • SIMMS (single inline memory module)
    • DIMMS (dual inline memory module)
    • RIMMS
ram configurations
Ram Configurations
  • The amount of RAM necessary in a computer often depends on the types of software you plan to use
  • The more RAM a computer has, the faster it
  • A software package will indicate the minimum amount of RAM it requires
cache speeds up process
Cache: speeds up process
  • Memory cache helps speed the processes of the computer because it stores used instructions and data
    • L1 cache has the smallest capacity
    • L2 cache has a larger capacity than L1
    • L3 cache exists only with L2 advanced transfer cache
  • Disk cache
read only memory
Read-only memory
  • ROM refers to memory chips storing permanent data
  • Data can’t be modified
  • ROM is nonvolatile
  • Rom chips are called firmware which contain permanently written data/info
  • A PROM (programmable) chip is a blank ROM which a programmer can write
flash memory
Flash Memory
  • A type of nonvolatile memory
  • Can be erased electronically and reprogrammed
  • Useful for updates
  • Flash memory cards store flash memory on a removable device instead of a chip
an aide to chips
An aide to chips
  • Complementary metal-oxide semiconductor (CMOS)
    • Technology that provides high speeds
    • Consumes little power
    • Uses battery power to retain info
memory access times
Memory Access Times
  • Access time is the time it takes the processor to read data/info
    • Directly effects how fast the computer runs
    • Nanoseconds and MHz are used to state access times
    • Accessing data from memory is faster than from hard disk
expansion slots and adapter cards
Expansion slots and adapter cards
  • The slot is a socket that holds adapter card
  • An adapter card is a circuit board (expansion card)
    • Enhances functions
    • Provides connections to peripherals
      • A peripheral connects to the system unit and is controlled by the processor
        • Examples: modems, printers, scanners
neat cards
Neat cards
  • A sound card enhances sound by allowing sound to be input thru a microphone and output thru speakers
  • A video card converts output info into a signal which displays an image on the screen
  • A modemcard allows computer to communicate via telephone lines, cable, etc..
  • A network card allows computer to access a network
pc cards and flash memory cards
Pc cards and Flash memory cards
  • A PC Card slot is an expansion slot that holds PC cards
    • A PC card adds memory, storage, sound, fax/modem & communications
    • PC cards are 1 type of flash memory card
      • A flash memory card allows users to transfer data from mobile devices to desktop computers
ports and connectors
The point where the peripheral connects to the system unit

Send data

The term jack is used to identify audio/video ports

Personal computers have ports in front

Others have in back

Joins a cable to a peripheral

2 genders of cables:

Male- 1+ exposed pins

Female-have matching holes to accept the pins

Same gender can’t connect

Gender changer- join same gender connectors

Ports and Connectors
serial ports
Serial Ports
  • Interface that connects a device to the system by transferring bit by bit
  • Connect devices that don’t require fast data
  • Examples: mouse, keyboard
  • The COM port is a type of serial port
parallel ports
Parallel Ports
  • Interface that connects devices by transferring more than 1 bit at a time
  • Printers are connected by this port
  • Also called a Centronics interface
usb ports
USB Ports
  • Short for Universal serial bus port
  • Can connect up to 127 different peripherals
  • Uses only 1 single connector type
  • To attach multiple peripherals use Daisy chain
    • The 1st USB device to the USB port on the computer, then the 2nd connects to 1st and so on
  • USB hub- plugs into USB port and contains multiple USB ports
special purpose ports
Special-Purpose Ports
  • Firewire- connect devices that require faster speeds
  • Midi- connects the system unit to a musical instrument
  • SCSI (small computer system interface)- connects disk drives and printers
  • IrDa- transmits data via infrared light waves
  • Bluetooth- transmits data using radio waves
  • Electrical channels that bits transfer on
  • Allows inside and outside devices to communicate with each other
  • Consists of 2 parts:
    • A data bus transfers actual data
    • An address bus transfers info where the data is
  • Bus width- the # of bits the computer can transmit at 1 time
word size and buses
Word Size and buses
  • The number of bits the processor can interpret and execute at a give time
  • Every bus has a clock speed (hertz)
  • 2 basic types of buses:
    • A system bus connects to main memory
    • An expansion bus connects to peripherals
expansion bus
Expansion Bus
  • Communicates with peripherals attached to adapter card
  • Types:
    • ISA (Industrial Standard Architecture)-most common
    • Local- a high speed expansion that connects higher speed devices
    • AGP (Accelerated Graphics Port)- designed to improve the speed with 3-D graphics
    • FireWire- eliminate the need to install cards
  • The expansion bus for a PC Card is the PC Card bus
power supply
Power Supply
  • Converts the wall outlet AC power into DC power
  • Near the supply is a fan to keep unit cool
  • Some external peripherals have an AC adapter, which is an external power supply
putting it all together
Putting it all together
  • Many components of the system unit influence the speed and power of the computer
  • These include:
    • Type of processor
    • Clock speed of the processor
    • The amount of RAM
    • Clock speed of the bus
chapter summary
Chapter Summary
  • Components of the system unit
  • Described how memory stores data/info
  • Discussed sequence of operations that occur when a computer executes an instruction