
Windows 8 and APIC timer (2012) - yuhong
https://social.msdn.microsoft.com/Forums/windowsdesktop/en-US/5d075378-a45f-433b-a3f7-73f974ec962f/windows-8-and-apic-timer?forum=wdk
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a2tech
What are you trying to point out with this thread? Its from 2012, contains
almost no technical information, and doesn't seem to show anyone behaving well
OR badly.

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vardump
Maybe because (IMHO) high precision timers (interrupts or events) on Windows
are still an imprecise mess.

It's quite painful in kernel mode to rely on a timer that ticks once per 16.5
ms or so. See KeSetTimerEx: [https://msdn.microsoft.com/en-
us/library/windows/hardware/ff...](https://msdn.microsoft.com/en-
us/library/windows/hardware/ff553292\(v=vs.85\).aspx).

You can of course change timer tick frequency to, say, 1 ms, but that
increases power consumption. And 1 ms is still pretty imprecise.

Windows 8 had some improvements, but timer still has jitter somewhere from the
requested value up to next system tick.

Same of course applies to user mode, of course there's even more jitter.

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yuhong
In this case, CPU-Z want to measure the current CPU frequency using the APIC
timer.

