I'm having a hard time reconciling the Anandtech definition of Tau:
> Tau is a timing variable. It dictates how long a processor should stay in PL2 mode before hitting a PL1 mode.
with the Intel one:
> Turbo Time Parameter (Tau): An averaging constant used for PL1 exponentional weighted moving average (EWMA) power calculation.
I'm assuming that this power calculation is calculated this way, in a similar way to how Unix load averages are. But the thing is that they are an exponentially weighted moving average. I understand why: moving averages need the storage of all the values over that time period and the EWMA only needs the last value of the moving average.
It's not exactly clear how tau relates to the constant used for the exponentially weighted moving average. Assuming I want to minimize the difference between the EWMA and the moving average over a time interval, there appear to be many valid ways to do so -- and this appears to depend on the statistical properties of the variable being averaged. But the Anandtech article shows it as if it's a constant time, which is subtly different.
> Tau is a timing variable. It dictates how long a processor should stay in PL2 mode before hitting a PL1 mode.
with the Intel one:
> Turbo Time Parameter (Tau): An averaging constant used for PL1 exponentional weighted moving average (EWMA) power calculation.
I'm assuming that this power calculation is calculated this way, in a similar way to how Unix load averages are. But the thing is that they are an exponentially weighted moving average. I understand why: moving averages need the storage of all the values over that time period and the EWMA only needs the last value of the moving average.
It's not exactly clear how tau relates to the constant used for the exponentially weighted moving average. Assuming I want to minimize the difference between the EWMA and the moving average over a time interval, there appear to be many valid ways to do so -- and this appears to depend on the statistical properties of the variable being averaged. But the Anandtech article shows it as if it's a constant time, which is subtly different.
Is this defined in more detail anywhere?