[ntp:questions] Win7 NTP-dev NMEA User Mode PPS, Freq_Mode Not Working

David Taylor david-taylor at blueyonder.co.uk.invalid
Fri Feb 28 09:49:26 UTC 2014

On 27/02/2014 16:44, Brian Inglis wrote:
> but offset, frequency, and therefore rootdisp kept increasing.
> Possibly clk_jitter, definitely sys_jitter and ref clock jitter
> were pegged at 0.976.../0.977, which seems to be a symptom of
> this runaway condition, and also occurs on stable if NTPd process
> is restarted rather than the system being restarted.
> Can not use signed kernel mode PPS driver (32 bit?) with my
> 64 bit PCI serial card drivers - it seems to be ignored.
> Followed your PPS serial instructions, for which thanks,
> and others around, and also fiddled a lot, with no indication
> anything had any effect.

The 0.977 milliseconds is a value seen because of the clock running at a 
maximum of about 1 kHz in Windows.

One clue may be in the system being restarted - NTP does try and 
determine some system characteristics when it starts up, but sometimes 
gets those values wrong.  This can result in inappropriate parameters 
being used, and NTP not working at its best.  I see that on my own 
Win-7/64 PC I have, in the system environment block:


I think that was purely because it gave better performance rather than 
being because a value was determined incorrectly at startup.

On one PC I did buy a 3rd-party serial card, with which the Dave Hart 
kernel-mode serialpps.sys didn't work.  That card required 3rd-party 
drivers, so that may be why.  SerialPPS.sys /has/ worked with a new 
computer with the COM port built into the motherboard.

However, even the user-mode driver built into Windows should work almost 
as well as the kernel-mode driver for detecting the DCD transition - 
it's only on a heavily-loaded system where the kernel=-mode driver helps 
a lot (as the user-mode will have deteriorated compared to a 
lightly-loaded system).  I take it that my Serial port LEDs program 
shows the DCD blinking on, when NTPd.exe is not running (and hence 
holding on to COMx).


There are both 32-bit and 64-bit versions of the driver.

Web: http://www.satsignal.eu

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