[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 
>>> curious)
>>> 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.
>>> Jason 
>> 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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