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From: John Baldwin <jhb@freebsd.org>
To: Adrian Chadd <adrian@freebsd.org>
Subject: Re: proposal: set default lid state to S3,
 performance/economy Cx states to Cmax
Date: Tue, 6 May 2014 16:37:29 -0400
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Cc: Kevin Oberman <rkoberman@gmail.com>,
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On Tuesday, May 06, 2014 2:08:35 pm Adrian Chadd wrote:
> On 5 May 2014 13:57, John Baldwin <jhb@freebsd.org> wrote:
> 
> > The user in question found this on 9-stable with the existing defaults as the
> > HPET was just plain broken on their system and that was unrelated to Cx states.
> > (Rather, Cx states were only involved because worries about them are why the
> > system chose to use HPET.  Had Cx states been enabled by default, they would
> > have had to disable those as well in addition to forcing LAPIC instead of
> > HPET.)
> 
> Hm. Sounds uncomfortable. How does Windows run on systems like this?
> Do the windows drivers just disable HPET and use LAPIC or worse for
> timing, and just ignore anything lower than C1?

I have no idea.  Maybe they use the RTC. :-/  Maybe the HPET on these systems
works if you use it "sparingly".  I believe OS X might have only used the HPET
to provide the "missing" LAPIC wakeups when entering Cx for example.  (Our current
eventtimer system wants to always use whichever timer it picks, not switch off
between them.)

-- 
John Baldwin