I have measured with the Now function. This is as far as I can see connected with the Win10 system clock, date time, which is very precise. Of course there is a standard deviation due to interrupts. But on average, when I measure 1.000 or even 10.000 times, it reproduces the same values.
When I measured my mainloop with the Now function I could see that a heavy CPU load degraded, or course, the throughput; and also here I measured rather stable and logical values with the Now function with a low load of the CPU (4 cores).
I have measured the loop and measurement itself. That takes only 1 uS per loop. So there is a negligible bias by the measurement (< 1 0/00).
It is too accidentally, that the time is always exactly (exactly!!!) 1 mS too much. Must be a mistake; either in the FPC implementation or in the Win 10 system call. I have no idea how I can check both of them. But I am sure that guys in this forum can do…..