Comment 38 for bug 132271

@samnmax: As I have already said, the bug does not lie within the kernel - you have a buggy ACPI BIOS. This is why you require NHC or similar in Windows. If your ACPI BIOS was correct, then frequency scaling would be working for you in both Linux and Windows.

speedstep_centrino is DEPRECATED. It will be removed altogether in future kernels. The only reason that it worked for you in Feisty is that the Feisty kernels had the Dothan frequency table patches added to speedstep_centrino.

The preferred way of setting frequency/voltage is via ACPI P-states, and this is how the kernel will do it in future (for Intel CPUs at least).

If for some reason you are unable to get a BIOS update to correct your buggy ACPI, your only option is to compile your own patched kernel, using the patches available at https://www.dedigentoo.org/trac/linux-phc/

Look on the bright side - my CPU (1.6 GHz) was stuck at 600 MHz until I got an updated BIOS to correct the ACPI bug.