[ntp:questions] Re: How application get precise time from Win NT/XP system time that synchronies to NTP

Martin Burnicki martin.burnicki at meinberg.de
Wed Mar 30 13:21:11 UTC 2005


Roger Chou ??? wrote:

> Martin,
> If my application polls the system time once every tick, i.e. 10
> millisecond, can I get nanosecond resolution and accuracy that NTP can
> provide?

As Terje already mentioned in his reply, the problem is in the Windows
implementation. Since the code is in the HAL, and the HAL is different for
uniprocessor machines and multiprocessor machines, the program behaves
differently if running on DMP or non-SMP machines.

If you try to interpolate using a timer callback function, that function may
be called immediately after a timer tick, or just a few milliseconds later,
if another application uses the multimedia timers as described in my
original post. Unfortunately I've found that there's still a jitter of 1
millisecond in the callback rate while the multimedia timers are active.

Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont

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