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Date: Sun, 30 Oct 2005 11:59:36 -0800
From: John-Mark Gurney <gurney_j@resnet.uoregon.edu>
To: Scott Long <scottl@samsco.org>
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Cc: Alexander Leidinger <Alexander@Leidinger.net>, freebsd-current@freebsd.org,
	David Xu <davidxu@freebsd.org>
Subject: Re: TSC instead of ACPI: powerd doesn't work anymore
	(to	be	expected?)
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Scott Long wrote this message on Sun, Oct 30, 2005 at 07:30 -0700:
> >Correct, but why is it felt the latency of the ACPI timer is an issue?
> >Of course we all want things to as fast as possible, but is that just an
> >abstract desire, or a real issue was run into?
> >
> 
> ACPI-fast requires an ioport read which takes about 1us (according to 
> Google).  Do that 1000 times a second and you have each CPU spending
> 1% of its time doing nothing but reading the clock.  Yikes.

Math correction: .1%...  1us * 1000 = 1ms, 1ms = .001s, .001 * 100% = .1%

-- 
  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."