[ntp:questions] stepping and slewing
serge.bets at NOSPAM.laposte.invalid
Sun May 13 17:46:30 UTC 2007
On Sunday, May 13, 2007 at 2:00:08 +0000, David L. Mills wrote:
> Be carefully advised that some kernels attempt to speed up the slew
> using an exponental average where the time constant depends on the
> offset. This introduces an additiona pole in the impulse response and
> can well explain the overshoot, even if adjtime() is called only once.
> If that is the case, the only way to behave properly is to remove this
> "feature" from the kernel.
The adjtime() slew here looks absolutely sane. A time/offset graph shows
a right oblique 500 PPM line all along, and immediate transitions at the
beginning, at the end, and even at slew direction changes.
Serge point Bets arobase laposte point net
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