[time-nuts] NTP jitter with Linux

Chris Albertson albertson.chris at gmail.com
Thu Apr 5 05:13:53 UTC 2012


On Wed, Apr 4, 2012 at 9:22 PM, Steve . <iteration69 at gmail.com> wrote:

> If the architecture has cache or wait states, it is still subject to be a
> moving target. I'm naturally skeptical on all architectures that have
> multiple channels, show me an architecture with cache or waits states and
> i'll show you a problem ( in regards to real time, that is)
>
> I stand firm that the only proper way to do this is with a 100%
> deterministic architecture.

..only proper way to do what?  The goal is to discipline the internal
software clock to GPS.  A typical application is a database server
that is running a web e-comerse site so that transactions get time
tagged.  So you would run a web, file or database server on a
deterministic, no cache micro controller?

Of course it would be easier to discipline a clock inside a purpose
built computer but that does not server the gol of time tagging
transactions in the server room

Or to say in another way.  If the goal is to deep a small micro
processor's clock in sync with GPS you don't need anything as complex
as NTP.   What NTP does well is that it can use reference loves that
are connected by slow and un-reliable data connections ilk the
Internet.  It works well over less than perfect links



Chris Albertson
Redondo Beach, California



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