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Cortex A8 Instruction Cycle Timing

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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0 barney vardanyan over 12 years ago

Note: This was originally posted on 11th April 2011 at http://forums.arm.com

I have made tests, and get very strange results.

the test is folowing

I have some cycle and nop intsructions in it.

first I have only one nop in cycle, it's takes 0.570 s on my board
then I add second nop instruction, and it's also takes 0.57 s. and it's true, becaues they executed in thy same cycle(pipeline 0 and pipeline 1)
then I continue to add nop instructions.
So when I got to 5-6 nop pair, I realize that they can't execute parraler
and after every nop instruction that I add increase the time of execution

So why after 5 nop, they don't executed parraler, IS there any idea?

here is the test file)
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0 barney vardanyan over 12 years ago

Note: This was originally posted on 11th April 2011 at http://forums.arm.com

I have made tests, and get very strange results.

the test is folowing

I have some cycle and nop intsructions in it.

first I have only one nop in cycle, it's takes 0.570 s on my board
then I add second nop instruction, and it's also takes 0.57 s. and it's true, becaues they executed in thy same cycle(pipeline 0 and pipeline 1)
then I continue to add nop instructions.
So when I got to 5-6 nop pair, I realize that they can't execute parraler
and after every nop instruction that I add increase the time of execution

So why after 5 nop, they don't executed parraler, IS there any idea?

here is the test file)
Cancel
Vote up 0 Vote down

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