The CPU

The CPU

1. Purpose

2. Factors that Effect Performance

   • Cores
   • Clock Speed
   • Cache Size
   • Processor Type

3. Fetch, Decode, Execute

   • Fetch
     • The first step the fetch-execute cycle carries out is fetching the instruction. The CPU fetches this from the main memory (the hard drive) and stores it in the CPU temporary memory, the immediate access store (the registers).
   • Decode
     • Once the instruction has been fetched, the CPU will need to understand the instruction to action it. This is called decoding.
   • Execute
     • When the instruction has been decoded, the CPU can carry out the action that is needed. This is called executing the instruction. The CPU is designed to understand a set of instructions - the instruction set.

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