Sets the speed of the CPU, if it supports multiple speeds, while
in the performance power profile.
Sets the speed of the CPU, if ...
This is from the ACPI manpage. You can view the current status of variables by typing "sysctl -a | grep acpi"
If you see the ones above (and you should if your processor supports them which yours does) you can change them.
Note: I am currently unable to discover what the documented values are for this sysctl or what they mean. If you could post what yours currently is... we might be able to guess and play around. Even better... I am going to look further on this issue -- you have been waiting long enough for any type of answer so this will do for the moment.
EDIT: sorry... this should have refered to .current_speed in the example above. And you can set it to the value in hw.acpi.cpu.performance_speed to get the max speed in from your system. Hope this helps.