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From: John Baldwin <jhb@freebsd.org>
To: freebsd-current@freebsd.org
Subject: Re: Leaving the Desktop Market
Date: Mon, 5 May 2014 11:42:38 -0400
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 (bigwig.baldwin.cx); Mon, 05 May 2014 12:26:10 -0400 (EDT)
Cc: Adrian Chadd <adrian@freebsd.org>,
 Nathan Whitehorn <nwhitehorn@freebsd.org>
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On Sunday, May 04, 2014 4:40:02 pm Adrian Chadd wrote:
> Hm, I was hoping for a little more discussion. Mostly around the
> "which older CPUs do we leave this on for?" crowd.
> 
> I have Pentium-M class hardware that I was going to spin up -HEAD on.
> 
> So I'll go install -HEAD on said older hardware and get a list of what
> does and doesn't work. I'm totally fine with disabling p4tcc and
> acpi_throttle if P states for cpu frequency adjustment are available.
> I just want to ensure that the temperature throttling stuff is going
> to get automatically engaged (by whichever magical BIOS/ACPI/SMI thing
> does it) and clock things down if the CPU gets way too hot.

The only things that should use throttling are really old machines where
ACPI asks the OS to do passive cooling by exposing the TC1 and TC2 constants.
(I have an old P4 laptop where this is the case, I think Pentium-M is too
new to need this.)  If we keep TCC at all, it should not be tied into cpufreq
but be a separate thing that only acpi_thermal.c uses.

-- 
John Baldwin