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Re: enhanced speed step on AMD64
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?
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.
>-- End of excerpt from Joerg Sonnenberger
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