[ntp:questions] Timekeeping broken on Windows XP with multimedia timer enabled (-M option)
David J Taylor
david-taylor at blueyonder.delete-this-bit.and-this-part.co.uk.invalid
Thu Jan 21 15:51:27 UTC 2010
"Martin Burnicki" <martin.burnicki at meinberg.de> wrote in message
news:mp2m27-dp3.ln1 at gateway.py.meinberg.de...
> AFAIK if the TSC is used then the clock frequency reported for QPC
> the CPU's clock full clock frequency, and IIRC then according to some MS
> docs the reported frequency does not even change when the CPU's clock is
> decreased for power saving. IMO that also wouldn't make much sense.
> From what I've seen the reported QPC clock frequency depends on which
> circuit is being used. Some months ago I've already posted what I had
> But of course I can not *guarantee* this is always correct ;-)
> In that article there are also some hints which Windows versions /
> packs use which timer to implement QPC. I've just reread that article
> found this perfectly matches what Alan has observed, i.e. Windows XP SP3
> should use the PM timer even if no /usepmtimer flag has been added in
> Windows' boot.ini.
> Of course it does not explain the problems Alan is observing.
Thanks, Martin. I'm beginning to wish I'd never asked, as I have Windows
XP SP3 here and yet the performance counter is running at 2.4GHz (Intel
E6600 dual-core). Or does the PM_Timer only apply to AMD systems?
The AMD Vista and Windows-7 desktop systems show 3.579...MHz, an Intel
Windows-7 portable 1.757MHz (PIT?), an Intel Vista portable 14.3MHz
(HPET), and an Intel Windows Vista Desktop 14.3MHz.
All frequencies you listed, and nothing which helps Alan. Seemed to have
a peculiar timer resolutions though - I never seen 3.906 ms or 1.953 ms.
What software is setting those?
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