Hardware

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Hardware

• Davis Rajkumar (6th), Chapter 2

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Overview

• Computer systems
• Memory
• Bits, bytes, and words
• Addressing memory
• Cache memory
• Processor
• Processor components
• Instruction set
• Machine cycle

• Input and output devices
• I/O ports and connectors
• Secondary storage
• Magnetic disks
• Backup
• Directory
• Communications hardware
• Linking components
• Summary

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Computer System

• Computer is a system
• Systems composed of components
• Components work together
• Computer system components
• Hardware Memory, processor, I/O, storage,
  communications
• Software
• Data
• Procedures
• People

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Memory

• Called main memory, primary storage, or memory
• Stores instructions and data for processor to use
  
• Composed of cells that store binary digits (bits)
  
• Retrieving bits is readRead does not change
  memory content
• Recording bits is writeWrite DOES change memory
  content, so text calls write a "destructive
  operation"
• Volatility
• Volatile memory requires power to retain bits
• Random access memory (RAM) volatile and
  read/write
• Read only memory (ROM) non-volatile and
  read-only

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Bits, Bytes Words

• Bit represented by state of memory cell
• Capacitor nearly full --gt 1
• Capacitor nearly empty --gt 0
• Group of bits represent
• Character
• Integer
• Floating point number
• Instruction
• Part of image, sound, or other data
• Size group of bits
• Bit 0 or 1
• Byte Eight bits
• Word Number of cells on row lineCommon word
  sizes 8, 16, 32, 64 bits

Figure 2.1 Memory Cell
Source http//www.aceshardware.com/read.jsp?id50
00172
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Addressing memory

• Memory addresses used for random access of
  content
• Each memory location has unique address
• Addresses sequential from 0 through number of
  cells less oneFig. 2.2 has 100 cells. 
  Addresses 00..99 
• Number of bits in addressable location depends on
  computer's word

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Cache Memory
Figure 2.3 Memory Hierarchy                    
                                                  
                                                  
                                            Sourc
e http//www.cse.lehigh.edu/mschulte/ece201-02/l
ect/lec14.ppt

• Cache increases speed for fetch operations
• High speed, near processor, and expensive
• Content usually guess about what is needed next

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Processor

• Processor, central processing unit (CPU), or main
  processor
• Controls manipulation of data based on
  instructions fetched from memory or cache
• Initiates action of other hardware components,
  which may also have specialized processors

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Processor Components
Figure 2.4 Simple CPU
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Instruction Set

• Each processor has set of instruction it can
  execute
• Instructions are binary numbers
• Instructions composed of two parts
• Opcode is operation code
• Operands are data used with opcode
• Mnemonics may be used for opcode when writing
  assembly programs

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Machine Cycle

• The machine cycle is a loop that gets, deciphers,
  and executes instructions.
• Repeat
• Fetch instruction
• Decode instruction
• Execute instruction
• Until halt instruction
• Execution of instructions may use routines in
  firmware called "microcode"
• HexMac Computer Simulation

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Input and Output Devices

• Input and output device allow a computer to
  interact with people and other machines
• Input devices enable entry of data or
  instructions
• Keyboard
• Scanner
• Mouse
• Speedometer
• Output devices provide user with result of
  processing
• Monitor
• Speakers
• Printer
• Throttle
• I/O makes feedback loop possible

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I/O Ports and Connectors
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Secondary Storage

• RAM relatively expensive and volatile
• Secondary storage
• Fast
• Accurate
• Inexpensive
• High-capacity
• Non-volatile
• Long-term storage
• To use content, must be read into memory
• To "view" content, must be read into memory and
  output to monitor or other output device
• Examples hard disks, diskettes, zip disks, CDs,
  DVDs, memory sticks

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Magnetic Disks

• Disk thin platter
• Made of metal (aluminum) or plastic (Mylar)
• Coated with microscopic layer of magnetic
  material
• Divided into track
• Tracks in same position on each surface from
  cylinder
• Tracks subdivided into sectors
• Read/write head on actuator arm for each surface
• Data transferred a sector at a time
• Time for head to reach desired track is seek time
  
• Time to rotate sector under head is rotation time

Source www.cs.wisc.edu/bart/ 537/lecturenotes/s2
2.html
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Backup
www.adrc.net/data-recovery/ tape-recovery.htm

• Backup makes copy of data in secondary storage
• Backups needed to prevent lose of data if hard
  drive inaccessible
• Usually tape or network storage area and tape
• Tertiary storage

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Directory

• Organizes data and instructions stored in
  secondary storage
• Outer track (track 0) holds directory
• Directory contains first sector and name for each
  file on disk
• Names assigned to files when they are created
• Files either stored in sequential sectors or
  sectors are linked by pointers
• To read file, name found in directory head moved
  to track with first sector and platter spun to
  place sector under head

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Communications Hardware

• Communications hardware enable networking
• Network applications include e-mail and Web
  browser
• Plain old telephone service uses modem
• DSL or cable use modem and network interface
  card (NIC)

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Linking Components

• Interface card translates data between device and
  system unit
• Interface card goes in expansion slot
• Interface card is integrated circuit
• Interface card may have buffer to store data
• Card may have processor to use direct access
  memory channel

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Summary
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Questions