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From: Michael Smith <msmith@freebsd.org>
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Date: Mon, 21 Jul 2003 04:31:23 -0700
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Subject: [acpi-jp 2480] Re: acpi and cpu performance states
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The CPU speed is not changed; that's controlled by the BIOS directly.

What the ACPI code does is use the chipset to limit the total CPU 
throughput
(effectively by performing fake DMA that keeps the CPU off the bus and 
thus
idle).

As has been pointed out a long time ago, this is less optimal than, 
say, rushing
to get the work done and then going to C2 or C3, but more suitable if 
you have
background processing going on a significant part of the time that's 
unrelated
to your interactive use of the machine,

  = Mike

On Monday, July 21, 2003, at 4:20 AM, Rudolph Pereira wrote:

> On Sun, Jul 20, 2003 at 03:45:55PM -0700, Nate Lawson wrote:
>> When I boot my laptop on acline, everything works normally.  When I 
>> unplug
>> the AC adapter, I get the offline event and the cpu drops back to a 
>> slower
>> speed (verified by benchmarks).  When I go back online, the 
>> performance
>> goes right back to its normal speed.
> On a related note, as I've reported (and at least someone else has 
> confirmed)
> cpu throttling doesn't work properly on some laptops. At least on my
> presario 720, even though I get the profile changed messages, the cpu
> speed itself is unchanged (according to x86info) when going from batt 
> <-> ac,
> whether I boot off ac or not. Furthermore, I actually have to look at
> the sysctls, or run apm to get freebsd to notice that something's
> changed (I suppose something's not being tickled until I do this)
>
>
--
Where am I, and what am I doing in this handbasket?

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The CPU speed is not changed; that's controlled by the BIOS directly.


What the ACPI code does is use the chipset to limit the total CPU
throughput

(effectively by performing fake DMA that keeps the CPU off the bus and
thus

idle).


As has been pointed out a long time ago, this is less optimal than,
say, rushing

to get the work done and then going to C2 or C3, but more suitable if
you have 

background processing going on a significant part of the time that's
unrelated

to your interactive use of the machine,


 = Mike


On Monday, July 21, 2003, at 4:20 AM, Rudolph Pereira wrote:


<excerpt>On Sun, Jul 20, 2003 at 03:45:55PM -0700, Nate Lawson wrote:

<excerpt>When I boot my laptop on acline, everything works normally. 
When I unplug

the AC adapter, I get the offline event and the cpu drops back to a
slower

speed (verified by benchmarks).  When I go back online, the performance

goes right back to its normal speed.

</excerpt>On a related note, as I've reported (and at least someone
else has confirmed) 

cpu throttling doesn't work properly on some laptops. At least on my

presario 720, even though I get the profile changed messages, the cpu

speed itself is unchanged (according to x86info) when going from batt
<<-> ac,

whether I boot off ac or not. Furthermore, I actually have to look at

the sysctls, or run apm to get freebsd to notice that something's

changed (I suppose something's not being tickled until I do this)



</excerpt><italic><fontfamily><param>Arial Narrow</param>--

Where am I, and what am I doing in this handbasket?</fontfamily></italic>


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