Re: enhanced speed step on AMD64

[bch%methodlogic.net@localhost]

On Mon, May 24, 2010 at 08:30:58PM +0300, Jukka Ruohonen wrote:
> On Mon, May 24, 2010 at 10:02:59AM -0700, Brian Buhrow wrote:
> >     Hello.   How hard would it be to implement #3 of your description?  Is
> > it getting easier as our acpi implementation matures and becomes more
> > stable and sophisticated?
> 
> Not that hard.

Is this something that I can particpate in from userland, either setting
or getting ACPI values?

> - Jukka.
> 
> > On May 24,  2:03pm, Joerg Sonnenberger wrote:
> > } Subject: Re: enhanced speed step on AMD64
> > } On Mon, May 24, 2010 at 12:12:45AM +0000, bch%methodlogic.net@localhost 
> > wrote:
> > } > Can anybody describe where "we" are at for supporting speedstep on CPUs
> > } > like the i7, then? Will it require an entire new framework to support? 
> > Can
> > } > somebody describe where the "problem" exists between this hardware and
> > } > the current NetBSD support for Speedstep on it? I'm interested both for
> > } > the practical matter of getting this CPU supported, and it's something
> > } > I just don't know anything about, so a "teachable moment" :)
> > } 
> > } Basically, frequency changes in Intel-land done in one of three ways:
> > } 
> > } (1) The original Speed Step. The frequency changes are done by magic
> > } calls into the BIOS and (AFAIK) a function of the chipset.
> > } 
> > } (2) EST until ~Core 2. Frequency and voltage are tabularised (older
> > } CPUs) or derived algorithmically from certain MSR (machine status
> > } registers). Change of the performance settings is done via MSR under
> > } application control.
> > } 
> > } (3) EST since late Core2. The MSRs are mostly discontinued and/or
> > } provide junk data. The kernel is supposed to use the ACPI Processor
> > } object and its method for this purpose. Doesn't work for all older model
> > } as it was often left out.
> > } 
> > } At the moment, (2) works best for the CPUs it can work on. (1) might or
> > } might not work. (3) is not supported.
> > } 
> > } Joerg
> > >-- End of excerpt from Joerg Sonnenberger
> > 
> > 

-- 
Brad Harder
Method Logic Digital Consulting
http://methodlogic.net
http://twitter.com/bcharder