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Multiple voltage levels for a Single Frequency in ARM A15 processors

maasa

Hi 

I am using a Samsung Exynos 5244 processor which has A15 and A7 cores. When I run an  application and get the power profiling, I see for a single constant frequency (say 1700MHz), the voltage varies between 0.913 V and 1.15V .  Can you please explain, why this happens ?

Also, I want to keep the voltage  constant for a single frequency.  Is there any way to fix the voltage level to a single constant value for a particular frequency.

Thanks,

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  • +1 Arm Employee Badge

    The available voltage and frequency levels and the control logic are not part of the ARM CPU core; it's external logic provided by the chipset manufacturer, so you'll have to ask on Samsung's developer forums for a definitive answer.

    In general frequency and voltage levels are related, but not 100% tied; specifically you need to change things in the right order to avoid signal corruption or power brownouts.

    • To increase frequency: set a higher voltage and let that stabilize *before* increasing frequency
    • To decrease frequency: set a lower frequency *before* reducing voltage

    I have no idea if this is what you are seeing though ...

    Pete

Reply
  • +1 Arm Employee Badge

    The available voltage and frequency levels and the control logic are not part of the ARM CPU core; it's external logic provided by the chipset manufacturer, so you'll have to ask on Samsung's developer forums for a definitive answer.

    In general frequency and voltage levels are related, but not 100% tied; specifically you need to change things in the right order to avoid signal corruption or power brownouts.

    • To increase frequency: set a higher voltage and let that stabilize *before* increasing frequency
    • To decrease frequency: set a lower frequency *before* reducing voltage

    I have no idea if this is what you are seeing though ...

    Pete

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