I was reading about the machine cycle. Everything was clear until I started with the execution of instructions. I know how an ALU and a CU work. I'm also aware of the process of fetching and decoding. But, I'm a little bit confused about the part that is responsible for executing instructions in a CPU.

Note: I've searched for an answer before asking. However, nothing was helpful enough.

  • $\begingroup$ 1. What exactly is your question? I don't see a question in the body of your post. 2. "I've searched and couldn't find anything" isn't very helpful. It would be better to tell us what useful information you've been able to find so far that was at least related, and provide some background on the parts you do understand and your current level of understanding. What textbooks have you tried reading? $\endgroup$
    – D.W.
    Nov 26, 2021 at 22:56

1 Answer 1

  • All the parts of the CPU are executing instructions at some point of time or the other.
  • The part(s) that is/are executing an instruction at a given time depends on the instruction being executed.
  • For example, in an add instruction, the ALU performs addition in the execute stage of the instruction cycle.
  • Through a process called pipelining, more than one instruction can be executed on a CPU. For example, data can be fetched in the Load stage while addition is being performed in the execute stage in the same cycle.
  • Optimizing compilers try to keep the whole CPU busy by reordering instructions such that all the parts of the CPU are busy most of the time.

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