Undervolting, Part 2

An update on the undervolting front. The PHC team has now used LaunchPad to provide a PPA (Personal Package Archive) that contains a standard Ubuntu desktop kernel recompiled so that the CPU frequency modules are run-time loadable and not built into the kernel. This meant that I could add their repository to my list of repositories, and then use a command line tool (apt-get) or GUI (synaptic) to automatically install that kernel. Sweet! I did so, and it installed properly, but the BIOS on my motherboard did not convince the PHC version of the acpi-cpufreq module that it was capable of supporting the calls to alter voltage assignments ("no such device"). Apparently this happens with some less-well-implemented BIOSes.

Fortune smiled, however. The old pathway (downloading the kernel source, modifying the deprecated but still active speedstep-centrino module, and recompiling & installing said module) worked just fine. The PHC PPA included a source repository, so the source I downloaded with apt-get was the source for the modified kernel I was running.

Now I'm back where I was before Ubuntu 9.04. Not the latest and greatest PHC mechanism, but undervolting nonetheless. I hope that my next system (five months away?) will be able to use the PHC acpi-cpufreq module. However, every choice affects everything else ... if I want to go with a 64-bit system, or a kernel with Physical Address Extension (PAE), in order to use more than ~3.2 GB of RAM, will the PHC team supply a corresponding kernel? Or will Ubuntu take the CPU modules out of the kernel for the 9.10 release? Stay tuned!