contemporary processors

• Definition of a processor?


  Part of a computer that executes instructions while letting programs run
• What is the ALU?


  Arithmetic Logic Unit, completes arithmetic and logic operations
• What is the CU?


  Control unit, has multiple uses

  Coordinates CPU activities

  Manages CPU/Device data flow

  Stores resulting data back into memory
• What are registers?


  Small memory cells that operate at high speeds
• What are the functions of registers?


  Temporary storage for data
• What are the main registers in a CPU?


  PC - holds address of next instruction to be executed

  ACC - stores results from calculations

  MAR - holds address of location that is read/written to

  MDR - temp stores data that has been read/needs to be written

  CIR - holds the current executing instruction, divides into opcode and operand
• What are buses?


  Sets of parallel wires which connect two or more components in the CPU
• What are the three different buses?


  Data, Control and Address
• What is the function of the data bus?


  Used for transporting data and instructions between components, is bi-directional
• What is the function of the address bus?


  Bus used to transmit memory addresses of where the data is to be sent or retrieved from
• What is the function of the control bus?


  Used to transmit control signals between internal and external components
• What are some examples of control signals?


  Bus request

  Bus grant

  Memory read/write

  Interrupt request

  Clock
• What is opcode?


  Specifies the type of instruction to be executed
• What is operand?


  Contains the data or address of the data where the operation is to be performed
• What are the stages of the FDE cycle?


  PC points to address of next instruction to be executed, which is copied to the MAR

  Address is placed on address bus

  Instruction stored on address bus is transferred using data bus, where the data is copied to the MDR

  The PC increments by 1

  Value in the MDR is copied to the CIR, where the instruction is decoded by being split into opcode and operand

  The instruction then executes, and the content of this execution is stored in the ACC
• What are the 3 factors effecting CPU performance/


  Clock Speed

  Cache

  Cores
• What is clock speed?


  The time taken for one clock cycle to complete
• What are cores? 


  Independent processors that are able to run it's own FDE cycle
• How do cores effect performance?


  A computer with multiple cores can complete more simultaneous FDE cycles, theoretically making processes faster.

  Not all programs are able to utilise multiple cores so the computer is not always faster
• What is cache?


  High speed memory located on the CPU that stores the most frequently executed instructions of the computer
• Describe Von-Neumann Architecture


  Basic components of the computer

  Has a shared memory and shared data bus
• Describe Harvard Architecture 


  Has physically separate memories for instructions and data

  Commonly used for embedded processors

  Each instruction has it's own bus
• Advantages to VN architecture?

  Cheaper to develop

  Programs can be optimised in size
• Advantages to Harvard Architecture?


  Quicker execution (data/instructions fetched in parallel)

  Memories can be different sizes (efficient space use)
• What is contemporary processing?


  Combination of Harvard and Von Neumann architecture, VN is used when working with data in man memory, Harvard is used to divide the cache
• What are RISC processors?


  Reduced Instruction Set Computers

  Each instruction is approximately one line of machine code and takes one clock cycle
• What are CISC processors?


  Complex Instruction Set Computers

  They try and accomplish tasks in as few lines of assembly code as possible

  Instructions are build into hardware
• RISC Properties?


  RISC:

  • More work for compiler
  • More RAM required to store code
• CISC properties?


  CISC:

  • Less work for compiler
  • Less RAM required
• What are multi-core systems?


  CPUs with multiple independent cores that can complete instructions separately (resulting in higher performance)
• What are parallel systems?

  Utilise threading to complete more tasks at once