1.1 Components of a computer

• multicore processor


  more than one processing unit in a single processor which can independantly process instructions at the same time
• Control Bus


  transmits control signals from control unit to other parts of the processor
• Data Bus


  carries data from one place to another

  bi-directional
• Address Bus


  carries the location address (register) where the data is going to or from
• Fetch Part of FDE


  address from the PC is copied to MAR

  instruction held at that address is copied to MDR by data bus

  at the same time the contents of PC increments by 1

  value held in MDR is copied to CIR
• Decode part of FDE

  contents of CIR is split into operand & opcode
• Execute part of FDE


  decoded instruction is executed
• CISC vs RISC


  RISC requires more RAM and takes one machine cycle. It is a fixed number of bytes and programs run faster due to simpler instructions CISC is more complex longer instruction set and takes many cycles to complete 1 instructions has variable number of bytes and many address modes
• Program Counter (PC)


  needed to store address of next instruction to be processes

  value is sent to MAR

  after value is sent, it increments
• MAR


  contains address of instruction to be accessed in memory

  sent from pc

  contains address of data to be access in memory

  sent from CIR
• Accumulator


  temporary storage for data being processed/during calculations - can be used as a buffer
• MDR


  contains instruction which has been accessed from memory by MAR and sent to CIR
• Control Unit


  decodes instructions

  sends control signals to coordinate movement of data through the processor or execute instruction

  controls buses
• Von Neumann Architecture


  instructions executed in linear sequence

  single control unit

  one instruction at a time

  uses FDE cycle

  program and data is stored together and in the same format

  single ALU
• Pipelineing


  concurrent process of completing FDE cycle of three separate instruction simultaneously

  holds appropriate data in a buffer in close proximity to the CPU until required

  increases speed of execution
• Factors to Increase Performance


  add more/faster RAM

  add graphics card

  upgrade to faster secondary storage

  update OS

  install lighter weight OS

  defragment hard disk

  check for viruses and spyware
• GPU/Graphics Card


  type of co-processor

  speeds up rendering of 3D graphics

  has built in programs for common graphics operations

  performs instruction on multiple pieces of data at one time

  independent processors in parallel
• Optical


  data read/written using a laser onto a reflective surface

  stored using pits and lands

  cheap to produce

  large capacity

  slow access speeds
• Explain why using a RISC processor rather than a CISC processor is likely to result in increased battery life

  RISC has a smaller instruction set (than CISC) Requires fewer transistors / less complex circuitry Means less power is required
• RAM


  volatile

  Used for storing parts of OS
• ROM


  non-volatile

  used for storing BIOS
• Solid Stage Storage


  stores data using semiconductors

  no moving parts required

  quick access speeds

  small capacity

  limited lifespan due to limited read/write
• Magnetic Storage


  stores data by altering magnetic field of small sections of tape/disk

  has a large capacity and is cheap

  best for storing operating systems, software and data
• Register


  temporary storage location inside the cpu used for single purpose, has faster access speed than RAM
• Harvard Architecture 


  separate physical memory addresses used for instructions and data

  separate buses are used for transferring data and instructions

  cpu can access instructions and read/write data at the same time
• Order of size of secondary storage devices

  Optical, SSD, Magnetic
• define volatile


  data lost when power is turned off
• Flash

  • non-volatile solid state storage
  • fastest
  • finite number of read/write cycles
  • robust
  • used to store BIOS
• Output device

  Any peripheral device that translates signals from the computer into a human-readable form
• Bus

  communication system that transfers data between components inside a computer
• Cheapest type of secondary storage

  magentic
• RISC or CISC: design is simpler and more power efficient making it ideal for portable devices

  RISC
• RISC

  design is simpler and more power efficient making it ideal for portable devices
• Explain why virtual storage is well-suited for storing backups.

  • Stored away from the computer so in case of disaster, data is not also damaged
  • All of the data can be backed up at the same time
  • Can be accessed from elsewhere / other machines
  • No physical space needed for backup hardware
  • No on site maintenance required