Re: Keeping a VERY accurate time (within a millisecond) - Networking

This is a discussion on Re: Keeping a VERY accurate time (within a millisecond) - Networking ; On Sat, 06 Sep 2008 12:03:05 -0500, Ignoramus10032 wrote: > I want my ubuntu servers to keep a VERY accurate time. That is, I want to > have a clock accurate to less than a millisecond. > > There is ...

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Thread: Re: Keeping a VERY accurate time (within a millisecond)

  1. Re: Keeping a VERY accurate time (within a millisecond)

    On Sat, 06 Sep 2008 12:03:05 -0500, Ignoramus10032 wrote:

    > I want my ubuntu servers to keep a VERY accurate time. That is, I want to
    > have a clock accurate to less than a millisecond.
    >
    > There is a business reason for it.
    >
    > NTP, when it works, lets me keep a time accurate to a few milliseconds,
    > which is great, but I would like to do better than that.


    Are you sure you want timebase ACCURACY? That is, a very close
    correlation to a standard time?

    Maybe you really want to measure DURATION? That is much easier and
    cheaper to do. A cheap timer/counter can give really astounding precision
    and accuracy of duration measurements. And that accuracy can be
    maintained over surprisingly long time periods.

    Keeping an accurate timebase, and still communicating over the internet is
    kind of contradictory.

    --
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    against American doctrine is that the Americans
    do not read their manuals nor do they feel
    any obligations to follow their doctrine.



  2. Re: Keeping a VERY accurate time (within a millisecond)

    On 2008-09-07, Joe User wrote:
    > On Sat, 06 Sep 2008 12:03:05 -0500, Ignoramus10032 wrote:
    >
    >> I want my ubuntu servers to keep a VERY accurate time. That is, I want to
    >> have a clock accurate to less than a millisecond.
    >>
    >> There is a business reason for it.
    >>
    >> NTP, when it works, lets me keep a time accurate to a few milliseconds,
    >> which is great, but I would like to do better than that.

    >
    > Are you sure you want timebase ACCURACY? That is, a very close
    > correlation to a standard time?


    Yes. To absolute time.

    > Maybe you really want to measure DURATION? That is much easier and
    > cheaper to do. A cheap timer/counter can give really astounding
    > precision and accuracy of duration measurements. And that accuracy
    > can be maintained over surprisingly long time periods.
    >
    > Keeping an accurate timebase, and still communicating over the internet is
    > kind of contradictory.


    Yes, I believe that it is difficult, but there is a good reason for
    it. I just do not want to go into details.

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  3. Re: Keeping a VERY accurate time (within a millisecond)

    Joe User writes:

    >On Sat, 06 Sep 2008 12:03:05 -0500, Ignoramus10032 wrote:


    >> I want my ubuntu servers to keep a VERY accurate time. That is, I want to
    >> have a clock accurate to less than a millisecond.
    >>
    >> There is a business reason for it.
    >>
    >> NTP, when it works, lets me keep a time accurate to a few milliseconds,
    >> which is great, but I would like to do better than that.


    >Are you sure you want timebase ACCURACY? That is, a very close
    >correlation to a standard time?


    >Maybe you really want to measure DURATION? That is much easier and
    >cheaper to do. A cheap timer/counter can give really astounding precision
    >and accuracy of duration measurements. And that accuracy can be
    >maintained over surprisingly long time periods.


    Well, no. One of the key problems with the cheap crystals in a PC is that
    they have typical drifts of 10s of PPM. Even 10PPM is 1 second per day.
    I do not know if you call that "astounding accuracy" or whether a day is a
    "surpisingly long time period".

    >Keeping an accurate timebase, and still communicating over the internet is
    >kind of contradictory.

    Not sure what you mean by this.





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