[ntp:questions] Timekeeping broken on Windows XP with multimedia timer enabled (-M option)

Terje Mathisen "terje.mathisen at tmsw.no" at ntp.org
Thu Jan 21 22:00:51 UTC 2010


Martin Burnicki wrote:
> Alan wrote:
>> However when I turn -M on the bottom line changes to Current 0.977 ms
>>
>> Is that really correct as even I can tell 0.977 is less than the
>> "minimun" 1.000 ms" in the previous line?
>
> I think 1 ms is just the nominal value and 0.977 is due to rounding errors
> or an inexact measurement interval.

Timer ticks on most versions of Win* are derived from the CMOS clock 
chip which can generate interrupts at any power of two rate, from 1 Hz 
to 32 KHz.

1024 Hz corresponds to ~977 us.

Terje

-- 
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"




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