[ntp:questions] Win7: ntpd adjusting time backwards

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Wed Dec 12 00:06:19 UTC 2012


Jeroen Mostert wrote:
> BlackLists wrote:
>> Jeroen Mostert wrote:
>>> I noticed the drift was ever-increasing, slowly but surely.
>>> Since I muddled with settings quite a bit, I stopped ntpd,
>>>   deleted ntp.drift and restarted it.
>>> The results are quite interesting.
>>> 56272 68581.536  0.022139147  2.356 0.006080932 0.008049 10
>>> 56272 68781.535  0.021885071  2.357 0.005698660 0.007537 10
>>> 56272 69311.535  0.020898356  2.359 0.005342012 0.007109 10
>>> 56272 71122.534  0.023597293  0.000 0.008392764 0.000000 6
>>> 56272 71458.536  0.013381279 39.825 0.012521981 0.000000 6 *
>>> 56272 71524.551  0.009503058 39.825 0.011793222 0.000000 6 *
>>> 56272 71527.552  0.000754424 39.825 0.011456980 0.000000 6 *
>>> 56272 71528.552  0.000233147 39.825 0.010722584 0.000000 6 *
>>> 56272 71930.577 -0.013119319 39.511 0.011085491 0.111141 6 *
>>> 56272 72003.578 -0.016005287 39.441 0.010419607 0.106838 6 *
>>> 56272 72207.579 -0.031178859 39.062 0.011125504 0.167193 6 *
>>> 56272 72331.588 -0.032740845 38.820 0.010421598 0.178267 6 *
>>> 56272 72607.596 -0.036786552 38.215 0.009852891 0.271267 7 *
>>> 56272 72611.597 -0.048063956 38.212 0.010042013 0.253749 7 *
>>> 56272 72667.599 -0.050119893 38.170 0.009421524 0.237821 7 *
>>> 56272 72960.613 -0.050045193 37.952 0.008819790 0.235492 6 *
>>> 56272 73291.594 -0.049274393 36.980 0.008257379 0.408236 6 *
>>> 56272 73419.587 -0.049355146 36.603 0.007731784 0.404411 6 *
>>     day,   second,      offset,  drift, est error, stability, poll
>>                                   comp
>>
>> I looked at several of the last few days of loopstats
>>   on a few machines; it appears your drift compensation
>>   change rate is perhaps hundreds of times what mine are?
>>
>> I'm not certain what that means, is the PC/Device experiencing
>>   large Temperature Swings, or Cpu/Core Frequency/Power Management?
>>
> Improbable. I've admittedly not measured, but the machine has
>   been running constantly for three days in a room with even
>   heating, with no significant change in load.
>  I don't think there's any way temperature could explain this
>   much drift.
> CPU frequency remains constant and power management has been
>  turned off.
>
> I suspect some driver or other is giving me trouble,
>   preventing ntpd from getting decent readings from the clock.
>  Or maybe the machine is just broken (clockwise, I mean),
>  I guess that happens.
>
> For kicks, I repeated the procedure -- stop ntpd, delete the
>  drift file, start ntpd, forcing it to do yet another drift
>  calibration. (The servers must love me.) The difference isn't
>  quite so dramatic, but still notable.
>
> 56272 76491.581 -0.039118819 30.383 0.004118758 0.429325 6
> 56272 76748.567 -0.038717153 29.790 0.003868185 0.453044 6
> 56272 76884.559 -0.035856775 29.500 0.003757023 0.436066 6
> 56272 76929.557 -0.023728814 29.436 0.005544073 0.408522 6
> 56272 77378.579 -0.030387567  0.000 0.010782393 0.000000 6
> 56272 77719.530  0.011532945 33.821 0.031973641 0.000000 6 *
> 56272 77719.532  0.012297079 33.821 0.029910596 0.000000 6 *
> 56272 77783.546 -0.000656742 33.821 0.028351163 0.000000 6 *
> 56272 77800.543 -0.000072661 33.821 0.026522332 0.000000 6 *
> 56272 78118.559  0.001651644 33.852 0.024816859 0.011068 6 *
> 56272 78127.560 -0.003217920 33.851 0.023277801 0.010371 6 *
> 56272 78193.560 -0.007368853 33.822 0.021823790 0.014112 6 *
> 56272 78197.561 -0.014632962 33.818 0.020575203 0.013258 6 *
> 56272 78257.562 -0.015837880 33.761 0.019251054 0.023555 7 *
> 56272 78989.594 -0.023846042 33.501 0.018228934 0.094564 7 *
> 56272 79047.605 -0.024689830 33.480 0.017055101 0.088777 7 *
>
> The moral of this story is, uhm... time is not on my side.

Those latest 22 minute {stdev (0.1357614218)}
 drift compensation values * appear to be changing < 13%
 of the 33 minute set above {stdev (1.0766335301)} ?

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