At 14.18 2005.02.28 +0000, you wrote:
>One possibility: the windows kernel thread scheduler works with a
>"clock" of 10ms. If your thread is pre-empted (ie, switched out of
>context), you will not get another time slice for at least 10ms.

you can lower it to 1ms if you make this WINMM.DLL call:

timeBeginPeriod(1);

and when you're finished:

timeEndPeriod(1);


>Consequently, all of the windows Wait* fuctions, which typically take a
>millisecond timespan as an argument, will not time to a resolution lower
>than 10ms. In fact, your wait call will happen on a multiple of 10ms.
>Over longer waits, and a lot of repeated waits, the effect tends to
>average out.
>
>You can test this easily with simple C++ code that fires a timer
>callback every 1 ms. If you use the QueryPerformanceCounter (and also
>QueryPerformanceFrequency), and write out the timespan since the last
>call, you'll see that despite the fact that you asked for 1ms, you get
>10 or 0, seemingly at random. A function like this will demonstrate:-

Even better use the Pentium+ TSC (Time Stamp Counter) register..

Greets,
TPM

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