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Date:      Thu, 6 May 2004 10:58:50 -0700 (PDT)
From:      Nate Lawson <nate@root.org>
To:        Jeffrey Katcher <jmkatcher@yahoo.com>
Cc:        acpi@freebsd.org
Subject:   Re: power savings and usb
Message-ID:  <20040506105607.J42462@root.org>
In-Reply-To: <20040506165526.41572.qmail@web41103.mail.yahoo.com>
References:  <20040506165526.41572.qmail@web41103.mail.yahoo.com>

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On Thu, 6 May 2004, Jeffrey Katcher wrote:
> On my T40, I see:
>    hw.acpi.cpu.cx_lowest: 0
>    hw.acpi.cpu.cx_supported: C1/1 C2/1 C3/85
>    hw.acpi.cpu.cx_history: 197586/0 0/0 0/0
> and the current power_profile script maintains cx_lowest as 0
> (i.e. not changing it on plug/unplug).  The 1st number in history is the only
> one to increment.

This means you're only using C1.  The value for cx_lowest is an index into
cx_supported.  (I'm changing this very soon to be more intuitive).

The reason it doesn't change on AC power transition is probably that you
don't have devd enabled.  Enable it in /etc/rc.conf.

> I can manually set cx_lowest to 2, not 3, then history changes to:
>    hw.acpi.cx_history: 0/0 2335/0 1710/30
> with the latter two incrementing.
>
> What does this mean?

This means your C3 is working and you have manually selected it.  Idling
demotes to C2 or C1 when your machine is active to prevent performance
degradation.

-Nate



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