[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.

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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