https://bugzilla.kernel.org/show_bug.cgi?id=16072 --- Comment #23 from Robert Bradbury <robert.bradbury@xxxxxxxxx> 2010-10-25 17:33:51 --- Thomas, you should have such a P4 machine plugged into a watt-meter as I currently have. I am (with the kernel modified back to the old p4-clockmod driver) able to detect a significant power savings as the machine scales itself back from 2.8 Ghz to lesser speed power savings [1]. p4-clockmod, as distributed prior to ~2.6.30, *did* work, in at least lowering power consumption when it did not need to be running at 2.8GHz (which on my machine might be only 2-4 hours/day). Mucking with the BIOS to add "real" ACPI support for reduced power consumption (if the CPU can even support it) is way beyond the capabilities of most users of Linux. I think the problem is that some kernel developer didn't like the responsiveness of a machine using p4-clockmod and changed the timing which allowed it to work quite effectively on many/most desktop machines [2]. Its simple for me -- I just change the code back to what worked when I upgrade kernels. But unless you are comfortable hacking the kernel (not something I consider likely with most Ubuntu users) that is difficult. Now if the kernel developers would like to release BIOS code for a HP Pavilion with a Pentium IV Prescott CPU which *does* support acpi-cpufreq and no longer generates the message: "cpufreq-core: initialization failed" then I would be willing to consider testing it. 1. The power savings dropping from 2.8 GHz to 350 MHz is 144 to 109 W or nearly 24%. 2. This is spite of the fact that p4-clockmod has a variety of information/adjustment params in /sys/devices/system/cpu/cpu0/cpufreq which could be set to manage the responsiveness of the machine for various workloads [3]. It seems to be a case of using a sledge-hammer to fix something that could have been fixed with a jeweler's screwdriver. 3. Which appear to be undocumented. So unless you know how to read the source code you cannot "tune" the machine easily. -- Configure bugmail: https://bugzilla.kernel.org/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are the assignee for the bug. -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
