Does anyone know if the kernel developers fixed this issue where acpi-cpufreq module has no effect for Pentium M processors speedstepping for laptops with a buggy bios, such as Dell for instance.
If so what kernel version was the fix in? I am currently am using Slackware 13.37 with a custom compiled kernel at 2.26.38. I am using a custom speedstep-centrino driver that was based on some changes that were made by some guys on the Arch Linux forum around 2006 or 2007 with some more processors added in by me last year. I am wanting to undervolt my processor (a Dothan 745) and so I am wanting to use acpi-cpufreq as it would make undervolting easier. I think I could also do it with the speedstep-centrino driver,but would have to hard code in the voltages. Also if anyone is still having problems with acpi-cpufreq, I'd be happy to give out my speedstep-centrino driver source file, as I saw a posting on some forum dated December, 2011 concerning this.

It looks like the only solution to this problem is to disassemble my bios' DSDT and reassemble a custom version and have Linux use that at boot time.

I'll just pass on a word of warning here.

I had huge issues with a HP6715S when I bought it first. Ubuntu took 5 hours to install; The fan roared constantly; suspend and hibernate didn't work, etc. etc.Compiles were drastically slow.

It was all in the kernel. To spare you the long and boring story, exhaust that option first. Don't rely on a distro kernel suiting your box. It's done for _nearly_every_ box.