Topic 1

• What is the purpose of the CPU


  To fetch, decode and execute instructions
• What is the FDE cycle?


  The cycle which the CPU runs to make a computer work
• What happens during the fetch stage of the cycle?


  The next instruction must be fetched from the RAM and the instruction is brought back to the CPU
• What happens during the decode stage of the cycle?


  Instruction decoding.
• What happens during the execute stage of the cycle?


  The CPU will carry out the instruction that was fetched
• What are the 4 key components of the CPU


  -Arithmetic Logic Unit (ALU)

  -Control Unit (CU)

  -Cache

  -Registers
• What is the function of the ALU


  Performs arithmetic operations and logical decisions
• What is the function of the CU


  Sends signals to control the flow of data and decodes instructions fetched from memory
• What is the function of the cache


  -Very small and fast memory used to provide quick access to frequently used data and instructions

  -Prevents the CPU from having to repeatedly fetch frequently used instructions from RAM
• Registers


  -Small, fast memory located in the CPU

  -Each register has its own specific purpose
• What are the 4 main registers


  Program counter (PC)

  Accumulator (ACC)

  Memory Address register (MAR)

  Memory Data Register (MDR)
• What does the Program Counter (PC) do


  -Holds the memory address of the next instructions to be executed
• What does the Memory Address Register (MAR) do


  Holds the memory address of where data or instructions are to be fetched from
• What does the Memory Data Register (MDR) do


  Stores the data or instruction which has been fetched from memory
• What does the Accumulator (ACC) do


  Stores the results of any calculations which have taken place in the Arithmetic Logic Unit (ALU)
• How does clock speed affect CPU performance


  The faster the clock speed the more instructions can be fetched and executed per second
• How does cache size affect CPU performance


  -Cache is used as temporary storage to provide quick access to a copy of frequently used instructions and data

  -The larger the cache size, the more frequently used instructions or data can be stored, speeding up performance
• How does number of cores affect CPU performance


  Multiple cores increase the performance of the CPU by working with the clock speed
• What is an embedded system


  A computer system with a single function, inside a larger mechanical unit
• Properties of embedded systems


  -They are small in size

  -They use less power than a general purpose computer

  They have a lower cost