[ntp:questions] Windows-8/64 kernel-mode PPS not producing expected jitter improvement
Mischanko, Edward T
Edward.Mischanko at arcelormittal.com
Sun Jan 20 20:54:19 UTC 2013
Jitter of .008 seems pretty good to me?
That's better than my FreeBSD box gets with PPS.
I realize that .000 would be preferable. ;-)
> I have been trying out the signed 64-bit serialpps.sys device driver
> made available as a result of bug report 2108:
> on a new 64-bit Windows-8 PC. However, I am not completely convinced
> that the driver is working as intended, and wonder whether anyone else
> has tried this driver? Without the driver, just using the DCD line
> alone, NTP is working as expected, with an averaged jitter of about 9
> microseconds. Adding in the 64-bit serialpps.sys and ensuring that the
> PPSAPI_DLLS environment variable was correctly set, the averaged jitter
> was unchanged, but the drift (frequency offset) was about 1 ppm greater.
> A new line appeared in the ntpq -p display:
> C:\Users\David>ntpq -p stamsund
> remote refid st t when poll reach delay offset
> oPPS(1) .PPS. 0 l 14 16 377 0.000 0.026
> *GPS_NMEA(1) .GPS. 0 l 13 16 377 0.000 -0.020
> +pixie .PPS. 1 u 20 32 377 0.311 0.046
> -Alta .PPS. 1 u 24 32 377 0.357 0.108
> +FEENIX .PPS. 1 u 7 32 377 0.310 0.049
> with the "o" indicating that the kernel-mode was working correctly.
> What I was expecting was that with the kernel-mode serialpps.sys, the
> jitter would at least be different, and all being well the jitter would
> be somewhat less than with user-mode time-stamping. That's what I've
> seen on other systems. I see nothing in the Event Log which suggests
> that NTP isn't working as expected, but neither am I seeing the expected
> Here is an extract from my ntp.conf:
> # ATOM driver with serialpps.sys
> server 127.127.22.1 minpoll 4 refid PPS flag3 1
> # NMEA serial port driver - Garmin GPS 18x LVC
> server 127.127.20.1 minpoll 4 mode 33 prefer
> I have tried flag3 as both 0 and 1, and there is no difference.
> It would be nice to mark this bug as VERIFIED, but with the results I
> have I am reluctant to do so.
> (Perhaps I should count myself lucky that the motherboard actually still
> has a COM port header!)
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