On 21.01.2012 19:41, David J Taylor wrote:
"Geir Guldstein" <[email protected]> wrote in message
news:[email protected]...
1 - You could try setting the /system/ environment variable
NTPD_USE_SYSTEM_CLOCK to "1" (or any value)
as this will force use of the native clock (to force off interpolation).
However, I'm not sure which version of NTP introduced this feature.
2 - I'm using NTP 4.2.7p241 which has produced excellent results on
Windows, so you may also like to try that.
Thanks David.
Regarding 1: 4.2.6p5 supports NTPD_USE_SYSTEM_CLOCK. However, I don't
think that it will make any difference. I see in the source code
(nt_clockstuff.c) that the event log message "using Windows clock
directly" (which I get in the case where NTP does *not* work properly)
indicates that ntpd already has disabled interpolation. Note that this
message is not generated in the case where NTP works reasonably well,
which means that it does use interpolation in this case.
The event log messages indicate that the device driver changes the
system clock's resolution:
Without device driver installed: "Windows clock precision 15.600 msec,
min. slew 6.410 ppm/s"
With device driver installed: "Windows clock precision 0.500 msec,
min. slew 6.410 ppm/s"
In nt_clockstuff.c I see that it is this precision that makes NTP
decide to enable or disable interpolation if no environment variables
have been set to control it.
Regarding 2: Thanks, I will try 4.2.7p241.
Geir
Geir,
Once you have 4.2.7p241 installed, it's worth trying with and without
the variable.
"Windows clock precision 0.500 msec" concerns me, because it suggests
that the driver is setting the Windows clock to 2 KHz, whereas the
normal range is up to 1 KHz maximum. Not sure how NTP will behave with a
clock running at twice the expected speed.....
Cheers,
David
I have now tested 4.2.7p241 with the device driver installed. I tested
both with and without NTPD_USE_SYSTEM_CLOCK. I see no difference when
running this version. I have now opened a support case with the
device/driver vendor.
Geir
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