Processor

• Central Processing Unit (CPU)

  • Very often installed as an integrated circuit on a single microchip
  • Responsible for the execution or processing of all the instructions and data in a computer application
• Components of the processor

  • Control Unit (CU)
  • Arithmetic and Logic Unit (ALU)
  • Registers
  • Buses
• Control Unit (CU)


  1. Fetches instructions from memory

  2. Decodes them

  3. Synchronizes the operations

  4. Sends signals to other parts of the computer
• Arithmetic and Logic Unit (ALU)


  • Where data is processed
  • Carries out arithmetic and logical operations
• Memory Unit (IAS)


  • Holds the data and instructions that are waiting to be processed
  • CPU fetches the data and instructions needed and stores them in the IAS to wait to be processed

  
• Bus


  • Parallel pathway for transmitting data and instructions
  • Connections between the processor, the memory unit, and input and output devices
  • Each wire in the bus transmits one bit of data
• Types of buses


  • Data bus (bidirectional)
  • Address bus (unidirectional)
  • Control bus (bidirectional)

  
• Data bus


  • Carries data from one location to another in processor (e.g. from CPU to memory and vice versa)
  • Wider bus means larger word length can be transported, improving computer's overall performance
• Universal serial bus (USB)


  Asynchronous serial data transmission method
• Address bus


  • Carries the address of a memory location (e.g. between the CPU and memory)
  • Wider bus means more memory locations can be directly addressed
• USB


  Becomes the standard method for transferring data between a computer and devices
• Control bus


  • Carries control signals around processor to synchronise the operation of the processor components (e.g. memory read/write completed)
  • Each line carries a different signal
• Registers


  • High-speed storage area within the processor (CPU)
  • Holds data or instructions temporarily when they are being processed
• USB cable


  • Four-wire shielded cable
  • Two wires used for power and the earth
  • Two wires used in the data transmission

  
• Universal serial bus (USB)
• Fetch-Decode-Execute cycle

  1. CPU fetches data and instructions from memory and stores them in registers

  2. Instructions are decoded so they can be interpreted

  3. Instructions are executed in logical sequence
• The interrupt process during the fetch-execute cycle
• Index register (IR)


  Microprocessor register used for modifying operand addresses during the run of a program, typically for doing array operations

  
• Index registers


  • Used for a special kind of indirect addressing where an immediate constant is added to the contents of the index register to form the address of the actual operand or data
• Status register


  Interpreted as independent bits/flags, each flag is set depending on an event, e.g. addition overflow/result of operation is zero
• The CPU has three main components, namely the control unit (CU), the arithmetic-logic unit (ALU) and registers.
• Arithmetic Logic Unit (ALU): This component performs mathematical calculations such as additions, subtractions, multiplications, divisions, etc.
• Control Unit (CU): The CU controls all activities within the processor by decoding instructions from memory and sending them to other parts of the computer system.
• Registers: These are small storage areas that hold data temporarily while it's being processed by the ALU.
• Control Unit (CU): The CU controls the flow of information between different parts of the computer system by sending signals that determine which instructions are executed when.
• Registers: These are small storage areas within the processor that hold frequently accessed data and instructions.
• Cache memory: A high-speed memory area located close to the processor that stores recently accessed data and instructions.
• Registers: These are small storage areas that hold frequently accessed information like instruction pointers, status flags, and temporary results.
• CPU Clock Speed: Measured in GHz, it determines how fast the CPU can execute instructions.
• Program Counter (PC): A register used to store the current instruction being executed.
• Accumulator: A temporary holding area for results produced during computations.
• Instruction Register (IR): Holds the currently executing instruction.
• Cache Memory: A high-speed memory buffer between RAM and CPU that stores recently accessed data for faster access.
• Program Counter (PC): A special register used to keep track of where the program counter is currently pointing to in memory.
• Instruction Register (IR): Another special register that holds the instruction currently being executed by the CPU.
• Cache Memory: A high-speed memory area used to store frequently accessed data and instructions.
• Main Memory: Also known as RAM or random access memory, this is where programs and data are stored during execution.
• Secondary Storage Devices: Used for storing large amounts of data permanently, including hard drives, solid state drives, optical discs, and magnetic tapes.
• Clock Cycle: The time taken for one complete cycle of the clock signal.
• Instruction Pointer (IP): Another name for Program Counter (PC).