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.


On 4 May 2014 10:07, Nathan Whitehorn <> wrote:
> On 05/04/14 10:05, Allan Jude wrote:
>> On 2014-05-04 11:47, Allan Jude wrote:
>>> On 2014-05-04 10:28, Matthias Apitz wrote:
>>>> El día Saturday, May 03, 2014 a las 04:59:48PM -0700, Kevin Oberman
>>>> escribió:
>>>>> On Sat, May 3, 2014 at 1:25 PM, Adrian Chadd <>
>>>>> wrote:
>>>>>> Set it to the lowest available Cx state that you see in dev.cpu.0 .
>>>>> Available is not required. Set it to C8. That guarantees that you will
>>>>> use
>>>>> the lowest available. The correct incantation in rc.conf is "Cmax".
>>>>> performance_cx_lowest="Cmax"
>>>>> economy_cx_lowest="Cmax"
>>>>> But, unless you want laggy performance, you will probably also want:
>>>>> hint.p4tcc.0.disabled=1
>>>>> hint.acpi_throttle.0.disabled=1
>>>>> in /boot/loader.conf. Low Cx states and TCC/throttling simply don't mix
>>>>> well and TCC is not effective, as mentioned earlier in this thread.
>>>> Re/ powerd I have in /etc/rc.conf:
>>>> # powerd
>>>> powerd_enable="YES"
>>>> powerd_flags="-a max -b adp"
>>>> #
>>>> performance_cx_lowest="Cmax"
>>>> economy_cx_lowest="Cmax"
>>>> (and the additional hint.* in /boot/loader.conf as well). Which process
>>>> 'performance_cx_lowest' and 'economy_cx_lowest' target exactly as config
>>>> values?
>>>> Thx
>>>>         matthias
>>> In a pretty unscientific test on my laptop (Lenovo T530 with Intel i5
>>> 3320M), setting hw.acpi.cpu.cx_lowest=C8 lowered power consumption at
>>> idle by about 3 watts, which adds about 30-45 minutes to my battery life
>>> during conservative usage.
>>> Using PCBSD 10, so hint.acpi_throttle.0.disabled=1 was already set
>>> (apparently solves some issue with powerd on some AMD systems)
>>> I have added hint.p4tcc.0.disabled=1 but not sure where to expect to see
>>> a difference.
>> I see the difference now, with the p4tcc stuff disabled, the lowest
>> cpufreq is now 1200mhz instead of 150mhz
> I just set the default for acpi_throttle and p4tcc in HEAD to disabled by
> adding these line to the default /boot/device.hints. If you want them back,
> editing your device.hints will restore them. This can be reverted if many
> people want throttling enabled by default, but all I have heard so far --
> and for the past many years -- is a unanimous chorus to turn it off.
> -Nathan
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