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From: louie@sayshell.umd.edu (Louis A. Mamakos)
Newsgroups: comp.protocols.time.ntp
Subject: Re: What means "drift" and "compliance" ?
Message-ID: <1991Feb19.195717.12530@ni.umd.edu>
Date: 19 Feb 91 19:57:17 GMT
References: <Feb.13.18.36.02.1991.1766@frogpond.rutgers.edu> <9102141633.AA20519@sayshell.umd.edu> <SCOTTH.91Feb19085248@harlie.corp.sgi.com>
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>Is 4096 the exact conversion, or is the complicated table-lookup scheme
>exact and 4096 an approximation? 

Yes, 4096 is the exact "conversion" to normal, everyday units.  There
is no "complicated table-lookup scheme".

>If 4096 is the exact conversion, why the
>lookup table scheme in the first place? The lookup scheme is not
>especially linear for large values of drift, and I suspect that it may be
>the cause of machines with large drift values being unable to sync.

I don't know what you're refering to when you cite a "lookup table
scheme".  There is no lookup table that has anything to do with the
drift value.  The drift value is used in the local clock algorithm to
represent the intrinisic drift of your host's clock, and to apply a
correction to it to keep its effective frequency correct.  NTP (and
ntpd) allows you to correct the phase of the clock as well as the
frequency.

Machines with large drift values either have broken hardware (i.e.
crummy crystals) or crummy software (i.e. missing clock interrupts).
The large drift value is just a symptom of the problem.

louie