Terje Mathisen <"terje.mathisen at tmsw.no"> wrote: > 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.
Ah, I know the features of the CMOS clock chip but I haven't been aware this chip is used to generate the timer tick IRQs. > 1024 Hz corresponds to ~977 us. Yep, and 64 Hz corresponds to 15.625 ms, the default system time increment up to Windows XP. Under Vista the clockres tool from sysinternals shows: Maximum timer interval: 15.600 ms Minimum timer interval: 0.500 ms Current timer interval: 1.000 ms So Vista seems to use a different timer for the timer tick, maybe the HPET which is also used for QPC under Vista? Martin -- Martin Burnicki Meinberg Funkuhren Bad Pyrmont Germany _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
