Fetch - execute registers
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Thread: Fetch - execute registers

  1. #1

    Fetch.Execute _ I know u want to help me!

    Hi AO,

    I have looked on the net and through forums but i havnt been able to find a good clear descriptions, it would be nice to see a nice diagram, i was hoping someone could make it a little more clear for me. I am doing an assignment on this topic, but i just cant get my head around it.

    How does the fetch execute cycle work using the registers and simple program in memory? You can use simple high level commands for this purpose but why wouldnt it be the case in reality?

    TIA
    The more you know, the less you understand!

  2. #2
    Just Another Geek
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    Most programs are build using high level languages. Compilers usually produce 'simple' code, mostly because it's easier (for the compiler) to optimize/produce. Another reason could be that the complex instruction executes using more clock cylces, compared to the total amount of clock cycles of a couple of simpler instructions.

    Does that make sense?

    As for the diagrams, have you looked around the Intel website? They've got really good instruction set "manuals" for their processors.
    Oliver's Law:
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  3. #3
    TY SirDice,

    I just had a look at the intel website, couldn't find what i was realy looking for, very specific explanations, i was after a more general one. I know its not good asking people to do you work for you, and im not, but i realy could do with a little more light being shed! . Let me put the question up, word for word so u can see what im being asked:

    Using an appropriate diagram, explain the fetch execute cycle showing registers used and simple program memory. You may use simple high level type commands for this purposebut explain why this would not be the case in reality.

    Im not asking anyone to do this for me, but hopefuly point me in the right direction!

    Regards

    Me



    TIA
    The more you know, the less you understand!

  4. #4
    Just Another Geek
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    It is Intel specific but these may help:
    http://developer.intel.com/design/pe...w.htm#sdm_vol1
    Oliver's Law:
    Experience is something you don't get until just after you need it.

  5. #5
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    im kinda blind at your question, but supposing i understood your question, you are asking how a processor works, right? basic hardware concepts, like A.S Tanenbaum books :P
    (BTW, go to your school library and look for "Computer Archicture" or something like that)

    take a look with this text diagram to see if its that you want:


    ------ begin of cycle ---

    - Fetch instruction from memory

    - decode instruction

    - execute instruction (since all operands are in registers we dont have a fetch operands phase)

    - updates registers and memory if appropriated (if there is return values presented by operation)

    - loop
    Meu sítio

    FORMAT C: Yes ...Yes??? ...Nooooo!!! ^C ^C ^C ^C ^C
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  6. #6
    Just Another Geek
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    Hmm. rereading it after cacosapo I'm not really sure I understood your question. I thought you meant the more complex cpu instructions that can do alot of things with one instruction as opposed to using a couple of simpler instructions to get the same thing done.
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  7. #7
    Senior Member
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    Originally posted here by SirDice
    Hmm. rereading it after cacosapo I'm not really sure I understood your question. I thought you meant the more complex cpu instructions that can do alot of things with one instruction as opposed to using a couple of simpler instructions to get the same thing done.
    I didnt start this thread SirDice. I was trying to get more info about the question

    i was just trying to answer thread start question. So i just posted the basic basic process diagram of instruction execution.
    Meu sítio

    FORMAT C: Yes ...Yes??? ...Nooooo!!! ^C ^C ^C ^C ^C
    If I die before I sleep, I pray the Lord my soul to encrypt.
    If I die before I wake, I pray the Lord my soul to brake.

  8. #8
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    after you've read Computer Architecture by A.S. tanenbaum you might wanna take a look at this (free) tool called
    IDaSS (http://www.xs4all.nl/~averschu/idass/). It's a simulator for digital circuits, wich includes a basic processor. with this your will be able to write your own instruction set and see it actually work in a simulation. It includes writing instructions for the state controller, ALU and memory operations.

    PM me if you want a working schematic for an (8-bit) processor, that works in IDaSS
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  9. #9
    Big up to the DUDE that program is top bannana!

    coco calm down mate

    im kinda blind at your question, but supposing i understood your question, you are asking how a processor works, right? basic hardware concepts, like A.S Tanenbaum books, try going to ur school library....
    get a life! i was asking for help on my coursework question that i couldnt get my head round, ive got the books from the library, but in my opinion they do not explian the cycle very well. Ive searched google, im sure theres something out there but i couldnt find it! posting on this forum is one of the many things ive tried to help me to understand it better (and if anyone has any more explanations or links id welcome them as i still donjt feel confident i can answer the question properly). But coco mate, please, in future dont be so cocky, it only pisses me off and it doesnt realy help anyone in the slightest

    peace
    The more you know, the less you understand!

  10. #10
    AO Guinness Monster MURACU's Avatar
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    Konshuss
    here are two links I found after doing a search for cpu architecture. Hope they help that is unless you have already seen them.
    cpu architecture
    simplified cpu architecture
    another simplified view

    PS I dont think cacosapo was being cocky I think it has more to do with him posting in a forgine language. Have to remember not everyone here speaks english as their first language.
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