Unit 6

• CPU features and enhancements

  ...

  • Separate fetch/execute cycles
  • Pipelining
  • Scalar processing
  • Superscalar processing
• What is pipelining?

  Processing of accumulating instructions from the processor through a pipeline. Stores and executes instructions in an orderly process. Fetches instructions one at a time
• Problems with early CPU architectures and solutions

  ...

  • Added hardware complexity slowed down other instructions
  • Slow data memory access could be reduced by increasing the amount of general purpose registers
  • Fixed format instruction words would allow instructions to be fetched and decoded independently and in parallel
• Multiple parallel execution units


  Multiple execution units permits simultaneous executions of several instructions
• Scalar and superscalar processing


  Scalar - Processes only one data item at a time

  
  

  Superscalar - It will fetch multiple instructions at once rather than one at a time
• What is multiprocessing

  The utilization of two or more CPUs in a single computer system

  
  

  Two ways of configuring:

  • Master-slave multiprocessing
  • Symmetrical multiprocessing
• Master-slave multiprocessing


  One processor will act as the master and the rest are the slaves. Whenever a program needs to be executed, the master processor will distribute the processes to the slave processors for execution
• Symmetrical multiprocessing


  All processors are given equal priority and each processor has their own job, they are independent from each other