[ntp:questions] Driver Help?
Richard B. Gilbert
rgilbert88 at comcast.net
Wed Jun 13 12:18:52 UTC 2007
Karl Denninger wrote:
> Karl Denninger wrote:
>> Jason Rabel wrote:
>>> What OS are you running, and what CDMA modem are you using? (Just
>>> Also from the info you gave it looks like it is using your CDMA
>>> source, but
>>> seeing the stratum at 16 I don't think you have had NTP run long
>>> enough to
>>> adjust the clock into sync.
>> FreeBSD 6 (and 7; I have both here); the modem is a Multitech MTCBA.
> Quick update on this.... it appears that while the timecode is being
> stuffed appropriately, the underlying NTPD daemon doesn't like it -
> after a half-hour or so (running with debug turned up) and watching it
> log things, it fails to lock on and resets the time source, dropping and
> restarting the clock.
> I assume this means it is unable to get "happy enough" with the
> stability of the timestamps to formulate a "solution", declares the
> clock "broken", and then restarts....... yes?
> The obvious question is "can a time source that outputs only with 1
> second resolution and only when polled generate
> sufficiently-high-quality reference time for the system to use it?"
> If the answer is "no", then the curtain needs to be drawn on this
> attempt. If the answer is "yes", then I need to figure out how to
> accomplish getting better input resolution I suspect - perhaps with a
> helper application that polls at a higher rate of speed (e.g. several
> times per second) and "stuffs" timecode events into the receive buffer
> (e.g. via a named pipe or similar)
Subject to correction by someone who knows what he's talking about the
answer is not just "no" but "HELL NO"!
The resolution of 1 second is a killer. This is going to make the
jitter a function of exactly when each poll is received. I doubt that
ntpd cares very much exactly when a poll is sent. If this device has a
PPS output, it might be useable. . . .
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