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My question is calculate how many CPU cycle takes to execute MOV A, 5 instruction. Describe each.

can anyone please explain me how this works. And the 5 is a value is it? Just explain me the main points.

As far as i know,

first,
-get the instruction from memory (one clock cycle)
-update instruction pointer(one clock cycle)
-decode the instruction to see what it does(one clock cycle)

i'm stuck after this.

zishe
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LekhAsh
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  • It depends on the architecture – rpax Jun 05 '14 at 06:59
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    Look at the documentation for that CPU, the number of cycles is clearly indicated for that simple operation. Eg http://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-optimization-manual.pdf – Déjà vu Jun 05 '14 at 07:00

1 Answers1

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I'm assuming you are talking about the x86 processors. This of course depends on the processor, but it usually takes 1 clock cycle from what i remember.

This is because instructions are executed in a pipeline. This means that while the processor is computing the result of an instruction, it is decoding the next and fetching the one before that, so that each part of the processor is busy doing something.

Usually the instructions that need data from memory or do complex calculations like multiplications or divisions take a longer time to execute.

You can also get the number of cycles with RDTSC https://www.ccsl.carleton.ca/~jamuir/rdtscpm1.pdf

George Nechifor
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