Process And Control Hardware

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A basic description of the CPU and the fetch-execute cycle.

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Process And Control Hardware

  1. 3. <ul><li>Controls all the operations in the CPU </li></ul><ul><ul><li>Transfers data to registers </li></ul></ul><ul><ul><li>Directs data to ALU for calculation </li></ul></ul><ul><li>Ensures correct paths for data transfer </li></ul><ul><li>Synchronisation with the system clock </li></ul>Click on image to go to the Fetch-Execute Cycle
  2. 4. <ul><li>Performs calculations </li></ul><ul><li>Tests logic functions </li></ul><ul><li>Determines relative relationships between values </li></ul>Click on image to go to the Fetch-Execute Cycle
  3. 5. <ul><li>Storage register </li></ul><ul><ul><li>Stores the next instruction to be executed </li></ul></ul><ul><li>Accumulator </li></ul><ul><ul><li>Stores the latest results from a calculation </li></ul></ul><ul><li>Address register </li></ul><ul><ul><li>Stores memory address locations </li></ul></ul><ul><li>Instruction register </li></ul><ul><ul><li>Stores instructions to be processed </li></ul></ul>Click on image to go to the Fetch-Execute Cycle
  4. 6. <ul><li>The system clock is an accurate, very fast electronic timer. </li></ul><ul><li>The faster the system clock the more instructions per second are executed. </li></ul>
  5. 7. <ul><li>Buses are pathways – separate wires / metallic strips which transport signals (data). </li></ul><ul><li>http://www.webopedia.com/TERM/b/bus.html </li></ul>
  6. 8. <ul><li>Fetch: </li></ul><ul><li>The instruction is fetched from memory. </li></ul><ul><li>Instructions are stored in registers . </li></ul><ul><li>Decode </li></ul><ul><li>the opcode is decoded by the CU so the instruction can be executed. </li></ul><ul><li>Execute </li></ul><ul><li>The instruction is executed, usually using the ALU . </li></ul><ul><li>Store </li></ul><ul><li>The result of the instruction is stored. </li></ul><ul><li>Note: this is a simplified explanation (what is required knowledge for the Preliminary course – see link for further detail). </li></ul><ul><li>http://en.wikipedia.org/wiki/Instruction_cycle </li></ul>
  7. 9. <ul><li>Decode: </li></ul><ul><ul><li>The typical instruction is divided into two parts: the Opcode and the Operand </li></ul></ul><ul><ul><li>The opcode is the instruction. </li></ul></ul><ul><ul><li>The operand is the data on which the instruction needs to be performed. </li></ul></ul><ul><li>In the simplified example below: </li></ul><ul><ul><ul><li>Add 10 </li></ul></ul></ul><ul><ul><li>Add would be the instruction (opcode). </li></ul></ul><ul><ul><li>10 would be the data (operand). </li></ul></ul>
  8. 10. <ul><li>More input / output devices </li></ul><ul><li>Increased processing speed </li></ul><ul><li>Larger memory (both primary and secondary) which is better for working with sound and graphics </li></ul>

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