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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,

  • +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

  • 0

    You are running your code on the chip or some kind of OS? If for example Linux (or Android on top of it), it is likely that the kernel modifies the core voltage in order to reduce power consumption.