CPU

• Fetch-Decode-Execute Cycle

  • Fetch: Instructions are fetched from RAM
  • Decode: The instructions are decoded
  • Execute: Control unit sends signals to relevant component for instruction to be carried out
• Von Neumann Architecture

  • Program counter: A register that tracks the RAM address of the next instruction to be fetched
  • Memory Address Register: A register that tracks the RAM address of the next instruction that is to be fetched
  • Memory Data Register: The MDR stores the instruction that has been transferred from RAM to the CPU
  • Accumulator: The Accumulator stores the result of mathematical or logical calculations
• Common CPU Components

  • Arithmetic Logic Unit: Performs mathematical and logical calculations
  • Cache: Fast memory that stores frequently used data
  • Registers: Temporary storage space for an instruction or address
  • Control Unit: Sends control signals to direct the operation of the CPU
• Clock Speed

  • How many times F-E cycle is performed per second
  • Measured in Gigahertz (GHz)
  • The higher the clock speed, the better the CPU Performance
• Overclocking

  • When clock speed is increased higher than recommended rate
  • Leads to better performance, but also to overheating which can damage the machine
• Underclocking

  • When clock speed is decreased lower than recommended rate
  • Leads to worse performance, but increases life span of machine
• Core

  A complete set of CPU components
• Multi-core CPU

  • Has more than one set of components within the same CPU
  • A computer with more cores will perform better as it can execute multiple instructions simultaneously
• If one core is waiting for another core to finish processing

  Performance may not increase at all
• Some software is not written to make use of multiple cores


  It will not run any faster
• Cache

  More cache, more storage for frequently used data, so more executions of F-E cycle per second