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Cortex A8 Instruction Cycle Timing

barney vardanyan
Note: This was originally posted on 17th March 2011 at http://forums.arm.com

Hi) sorry for bad English

I need to count latency for two instruction, and all I have is the arm cortex A 8 documantation(charter 16) !
but I have no idea how can do this work using that documantation(
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    Note: This was originally posted on 28th April 2011 at http://forums.arm.com


    For branch :
    I'm do not know anything about the first stage of the ARM pipeline.
    I don't know what you want to do.


    My purpose, I think, is just simple. I want to develop a tool to count the number of cycles to execute a short source code.

    Therefore, I have studied pipeline of Cortex-A8, branch penalty and the latency of 2 continuous instructions.

    I have found many things that I hardly understand. I hope, together, we can make them clear.


    But, I think that there is no way to know just with a code source if a (conditional) branch will be mispredict or not.


    Yes, I agree with you. To know whether a branch is mispredicted or not, we need to check CPRS, SPSR register, check PC address ...

    I don't have a board or a Cortex-A8, I am just a man of theory :((
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  • 0
    Note: This was originally posted on 28th April 2011 at http://forums.arm.com


    For branch :
    I'm do not know anything about the first stage of the ARM pipeline.
    I don't know what you want to do.


    My purpose, I think, is just simple. I want to develop a tool to count the number of cycles to execute a short source code.

    Therefore, I have studied pipeline of Cortex-A8, branch penalty and the latency of 2 continuous instructions.

    I have found many things that I hardly understand. I hope, together, we can make them clear.


    But, I think that there is no way to know just with a code source if a (conditional) branch will be mispredict or not.


    Yes, I agree with you. To know whether a branch is mispredicted or not, we need to check CPRS, SPSR register, check PC address ...

    I don't have a board or a Cortex-A8, I am just a man of theory :((
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