Greg Smith wrote:

Anyway, the patch does now includes several examples and a short primer on
PC clock hardware, to help guide what good results look like and why they've
been impossible to obtain in the past.  That's a bit Linux-centric, but the
hardware described covers almost all systems using Intel or AMD processors.
Only difference with most other operating systems is how aggressively they
have adopted newer timer hardware.  At least this gives a way to measure all
of them.

N.B.: Windows has at least two clock APIs, timeGetTime and QueryPerformanceCounters (and probably more, these days). They rely on different hardware clocks, and can get out of sync with each other; meanwhile, QueryPerformanceCounters can get out of sync with itself on (older?) multi-CPU boards.

So if you're doing high-res timing, it's good to make sure you aren't relying on two different clocks in different places... I ran into this with MIDI drivers years ago; and wrote a doc:

and a clock-testing utility:

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