F14 cpuspeed / ondemand broken?

[Steven Haigh]

On 4/01/2011 12:29 AM, Steven Haigh wrote:
> On 4/01/2011 12:08 AM, Adam Williamson wrote:
>> On Fri, 2010-12-31 at 08:49 -0600, Richard Shaw wrote:
>>
>>> I wish I could find the site where I got this information as my
>>> recollection of it is a bit hazy but part of your problem may be that
>>> the p4-clockmod and ondemand are more or less incompatible. I remember
>>> reading something on kerneltrap or something. Basically the latency of
>>> changing frequencies are so bad with p4-clockmod that ondemand gives
>>> up on it or something like that. I think I could force it to work on
>>> my Celeron based EEEPC by manually setting the governor something like
>>> this[1]:
>>
>> yeah, I recall p4-clockmod being called out as problematic in several
>> ways by some kernel dev or other, but like you I can't recall the
>> details :/
>>
>> on my system which wants to use p4-clockmod, I just blacklist it and run
>> full steam ahead all the time.
>
> What I don't understand is that if the CPU supports ACPI, the mainboard
> supports ACPI, why can't we throttle the CPU using ACPI?
>
>   From /proc/cpuinfo:
> flags           : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca
> cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm
> constant_tsc pebs bts pni dtes64 monitor ds_cpl cid cx16 xtpr lahf_lm
>

I think I may have answered my own question:

http://ark.intel.com/Product.aspx?id=27512&processor=820&spec-codes=SL88T,SL8CP

 From this, it states the CPU doesn't support Enhanced SpeedStep or 
Demand Based Switching - both of which I assume is what acpi-cpufreq 
uses to reduce power usage on the CPUs which support these features.

-- 
Steven Haigh

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