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From: Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP>
Newsgroups: comp.lang.ada
Subject: Re: how to analyze clock drift
Date: Wed, 19 Nov 2014 02:10:36 +0000 (UTC)
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Date: 2014-11-19T02:10:36+00:00
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On 2014-11-18, Emanuel Berg <embe8573@student.uu.se> wrote:
> I have a long list of samples of clock readings. It
> "should" be periodical, by 1 ms, but of course it
> isn't. The data is in nanoseconds.
>

How are you gathering the data ?

Is the data being stored in a hardware register as the result of some
trigger until it can be collected by your program or is your collector
directly gathering the clock reading ?

IOW, how do you know the same amount of _actual_ real world time has
elapsed between the clock being sampled ?

What's the hardware and software environment ? Is your code running
on bare metal ?

If you are gathering the data directly, instead of via some hardware
buffer, are any instruction/data caches enabled on your processor ?

> Anyone knows how I can apply some math/stat method to
> find out the average drift, and/or if the drift will
> average out, or just about any conclusions you can get
> out of the material?
>

Before you get that far, you need to make sure you are gathering
what you think you are gathering.

Simon.

-- 
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Microsoft: Bringing you 1980s technology to a 21st century world