[ntp:questions] Re: NTP stepping issue

Brian Utterback Brian.Utterback at Sun.removeme.COM
Wed Oct 20 12:47:55 UTC 2004


David L. Mills wrote:
> Robert,
> 
> You are not going to like this answer. I mentioned awhile back that 
> Solaris, at least, had fiddled with the adjtime() syscall to speed up 
> convergence for large adjustments, effectively adding an additional pole 
> to the carefully crafted impulse response built into ntpd. The result 
> expected is serious overshoot at large offsets, just as you describe. 
> There is no help for it other than to use the kernel modifications, but 
> the existing modifications were designed only for offsets less than 0.5 
> second.
> 
> I don't know what system you are using, but if it slews faster than 500 
> PPM, expect trouble.

Dave, correct me if I am wrong, but isn't a 50% overslew expected even if
the slew rate is less than 500PPM as required? IIRC, this is one of the tests
to see if the kernel PLL is working correctly.
-- 
blu

Power corrupts. PowerPoint corrupts absolutely.
--------------------------------------------------------------------------------
Brian Utterback - OP/N1 Revenue Product Engineering, Sun Microsystems, Inc.
Ph/VM: 877-259-7345, Em:brian.utterback-at-ess-you-enn-dot-kom



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