[ntp:questions] How to control accuracy of GetSystemTimeAsFileTime?

johumohu at yahoo.com johumohu at yahoo.com
Wed May 13 20:12:25 UTC 2009

The theoretical precision of  GetSystemTimeAsFileTime() or equivalent
procs is 100 nanoseconds. However my tests show the accuracy is
minimum 1 millisecond and all updates are done in multiples of 1
millisecond. I ran the tests on a new consumer-type PC desktop (quad
processor)  and a new consumer-type laptop (dual processor), both with
Vista, the test results were similar on both.

Normally, the system time count is updated every 1 millisecond, but
there are some long intervals when the system time is updated
consistently every 16 milliseconds (one tick). I suspect it has to do
with power management because these cases seem to happen when there is
no input through the keyboard or mouse for extended period of time. My
power management is configured to NEVER put processor to sleep, and I
have not seen any other power managament parameter related to this

Does anybody know how to force the system time to be updated every 1
millisecond? What to check for?

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