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

    Hi,

    Are you using the models of the ARM11 CPUs delivered as part of RVDS3.0?

    If so, they are based on ARMulator models which stopped being cycle accurate
    after v5. Some v6 instructions had approximate cycle counts added, but the complexity
    of the pipeline meant that ARMulator could only provide a static calculation. As a result,
    none of the v6 instructions in a model can be relied upon to provide a correct cycle
    count.
Reply
  • Arm Employee Badge
    Note: This was originally posted on 4th February 2013 at http://forums.arm.com

    Hi,

    Are you using the models of the ARM11 CPUs delivered as part of RVDS3.0?

    If so, they are based on ARMulator models which stopped being cycle accurate
    after v5. Some v6 instructions had approximate cycle counts added, but the complexity
    of the pipeline meant that ARMulator could only provide a static calculation. As a result,
    none of the v6 instructions in a model can be relied upon to provide a correct cycle
    count.
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