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

Terje Mathisen terje.mathisen at hda.hydro.com
Wed Mar 30 10:03:23 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?

No. No way. Never.

What you might get is millisecond.

WinNT started out with a beautiful system clock definition, using 100 ps 
(yes, 0.1 ns!) as the resolution, then they immediately destroyed it by 
a combination of two mistakes:

1) Interpolation between ticks simply isn't done.

2) The clock is in the HAL (Hardware Abstraction Layer) below the OS, so 
even a regular kernel driver cannot fix it.

Terje

-- 
- <Terje.Mathisen at hda.hydro.com>
"almost all programming can be viewed as an exercise in caching"



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