Factors Affecting CPU Performance

• CPU performance

  The speed at which a Central Processing Unit (CPU) executes code
• Factors affecting CPU performance

  • Clock speed
  • Cores
  • Cache memory
  • Pipelining
  • Idle processor
• Clock speed

  • The CPU's clock sends a pulse at fixed intervals to trigger the next stage of the fetch, decode, execute (FDE) cycle
  • The higher the clock speed, the more pulses are sent per second, so more instructions can be executed in the same amount of time
• Cores

  • Each core of a CPU is capable of processing instructions independently
  • Each core has its own Control Unit (CU), and Arithmetic and Logic Unit (ALU), but the cores share access to cache and main memory
  • Multiple cores allows a CPU to process multiple instructions at the same time
• Cache memory

  • Cache memory is a small amount of very fast memory inside the CPU
  • In comparison to the cache, accessing the Random Access Memory (RAM) is a very slow operation
  • By storing frequently accessed data and instructions in cache memory we can avoid the process of accessing the RAM
• Pipelining

  A feature which allows more processor operations to take place in less time
• Idle processor


  Processors typically complete one instruction before moving on to the next, meaning parts of the processor are idle while the instruction is completed
• Effect of pipelining

  Pipelines ensure as much of the processor is in use all at one time and increase efficiency of the computer system
• Types of pipeline

  • Instruction Pipeline
  • Arithmetic Pipeline
• Instruction pipeline

  • The instruction pipeline will pre-fetch the next instruction and data and store it in a register
  • As one instruction leaves the current instruction register (CIR), the next one is ready to be loaded and decoded
  • At any given point, there are instructions being fetched, decoded and executed
• Arithmetic pipeline

  • The arithmetic pipeline divides up an arithmetic operation into its individual steps
  • Each step is performed overlapping the next step