Computer Science Comp 1 CPU

Computer Science Comp 1 CPU

1. Factors affecting CPU

   • Cache size - more space to hold instructions
   • Clock speed - more cycles per sec
   • Number of Cores - more instructions can be executed

2. Fetch/Decode/Execute Cycle

   • Fetch - Receive instruction from a memory address
     • Decode- Identify the operation from the instruction
       • Execute - Link up parts of the CPU needed to carry out operation

3. Roles of the CPU

   • • Receives instructions from the computer
   • • Processes received instructions
   • • Executes programs
   • • Manages computer hardware
   • • Handles communication between components

4. Components

   • Buses - Parallel wires connecting 2+ independent components of a computer system to pass signals.
     • Address Bus - sends the addresses (locations) of data from the processor to main memory. 1 way.
     • Data Bus - sends the data for processing/storing to and from main memory. 2 way
     • Control Bus - sends signals to and from the control unit to other parts. 2 way
   • Control Unit - to send control signals between different internal components
   • Arithmetic Logic Unit - to perform arithmetic and logic calculations using +,-, AND, OR
   • Cache - high speed memory used to store data before it is processed by the CPU
   • Peripherals - any devices, not directly connected to the CPU e.g. Mouse, keyboard, printer, hard disk.
   • Secondary Storage devices - external devices used for storage e.g. Hard disk drive, Solid State Drive, Flash Memory, DVD-R and Blu-Ray
   • Embedded systems aka firmware are combinations of hardware and software that perform a specific function or perform specific functions within a larger system. Central heating control system, dish washer, washing machine, digital TV.

5. Cache

   • Level 1 cache is the fastest and stored on the CPU
   • Level 2 is also on the CPU, but may serve several cores
   • Level 3 is separate from the CPU but closer than the RAM

6. Registers

   • MAR - Memory Address Register - records the memory address of the data to be fetched or stored
   • MDR - Memory Data Register - stores data after being fetched from Main Memory
   • PC - Program Counter - contains the memory address of the next instruction
   • CIR - Current Instruction Register - Copied from the MDR, holds the current instruction to be executed
   • ACC - Accumulator - stores the result of calculations