Re: enhanced speed step on AMD64

[buhrow%lothlorien.nfbcal.org@localhost (Brian Buhrow)]

        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?
-Brian
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