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Arm11 clock

korner korner
Note: This was originally posted on 13th October 2008 at http://forums.arm.com

Hello,

Does anyone know if there is a timestamp clock in Arm? Something like the RDTSC in intel?
Or some other high frequency clock?
I need a clock to mesure performance of my linux kernel (and I use the RTC for something else).

Thanks everyone!
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  • 0 Arm Employee Badge
    Note: This was originally posted on 13th October 2008 at http://forums.arm.com

    I'm surprised that CP15 doesn't do what you want, but I must admit that I haven't used the performance monitor stuff before.

    It's likely that your processor has counter peripherals which may be configurable to do what you want, but you'll have to look at the documentation for the particular chip you have as I don't think that's architectural.

    On another note: RTCs typically have an accuracy of milliseconds at best, and many RTCs only give a resolution of 1 second anyway. Does the interrupt latency really matter in such a situation? Consider a very slow system: A 100MHz ARM11 core with a 1000 cycle interrupt latency. 1000 cycles at 100MHz is just 10 microseconds.
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  • 0 Arm Employee Badge
    Note: This was originally posted on 13th October 2008 at http://forums.arm.com

    I'm surprised that CP15 doesn't do what you want, but I must admit that I haven't used the performance monitor stuff before.

    It's likely that your processor has counter peripherals which may be configurable to do what you want, but you'll have to look at the documentation for the particular chip you have as I don't think that's architectural.

    On another note: RTCs typically have an accuracy of milliseconds at best, and many RTCs only give a resolution of 1 second anyway. Does the interrupt latency really matter in such a situation? Consider a very slow system: A 100MHz ARM11 core with a 1000 cycle interrupt latency. 1000 cycles at 100MHz is just 10 microseconds.
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