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wrong cycle timing of instructions on ARM11

chandrakala reddy
Note: This was originally posted on 4th February 2013 at http://forums.arm.com

Hi,

Iam using RVDS3.0 for ARM11. some of the instructions are not executing in the time specified by the ARM documentation. for example, according to ARM documents, SMLAD instruction has to take 1 cycle for execution and 2 stalls if the result is immediatly used. but in real time, it is taking 2 cycles for execution. is it a bug on RVDS3.0 or am i missing any thing here. can any one please help me out.

Regards,
Chandrakala
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  • Arm Employee Badge
    Note: This was originally posted on 4th February 2013 at http://forums.arm.com

    Couple of possibilities....
    * You could just be measuring it incorrect - you haven't given any details of how you are doing this
    * It could be a register dependency on one of the inputs
    * It could be something like a cache or TLB miss.

    I would have thought the second one is the most likely.
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  • Arm Employee Badge
    Note: This was originally posted on 4th February 2013 at http://forums.arm.com

    Couple of possibilities....
    * You could just be measuring it incorrect - you haven't given any details of how you are doing this
    * It could be a register dependency on one of the inputs
    * It could be something like a cache or TLB miss.

    I would have thought the second one is the most likely.
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