Date: Wed, 02 Feb 2005 19:17:13 +0000 From: Colin Percival <cperciva@freebsd.org> To: Nate Lawson <nate@root.org> Cc: current@freebsd.org Subject: Re: New cpufreq framework and drivers Message-ID: <42012739.9080501@freebsd.org> In-Reply-To: <41FFB53B.3020907@root.org> References: <41FFB53B.3020907@root.org>
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Nate Lawson wrote: > Hardware drivers are of two types, absolute > and relative. SpeedStep, Powernow, etc. are absolute drivers in that > they set the cpu's base frequency. ACPI throttling, Longrun, etc. are > relative drivers that reduce the processor's clock to a fraction of its > current base (i.e., they have an additive effect.) If my first glance at the patch is correct, this would have my laptop (a 1.4GHz Pentium M) reporting the availability of the frequencies 600MHz, 800MHz, etc. from enhanced speedstep, along with the frequencies 300MHz, 400MHz, 500MHz, and 700MHz obtained via 50% clock throttling. While this in itself is entirely valid, a clock speed of 700MHz obtained by running the processor at 1400MHz with a 50% "duty cycle" would draw more power than a clock speed of 800MHz obtained by running the processor at 800MHz with a lower voltage; is there any mechanism to inform userland daemons of such oddities? I would hate to see a daemon lowering the clock speed from 800MHz to 700MHz in an attempt to save power... Colin Percival
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