Originally written by Thomas Schreck, this panel plugin shows information about the CPU governor and frequencies supported and used by your system. At the moment, changing any of these settings is not supported by this plugin but might be implemented in future releases.
From the configuration dialog, which is available by right-clicking on the panel widget, select the CPU which you want to monitor in the panel. Instead of showing values for a single CPU, you can alternatively choose minimum, average or maximum, which might make more sense on a multi-core system. If your system is using the Intel pstate driver, the current maximum will be chosen by default, as this is what other monitoring applications like i7z show as the current real performance.
The remaining options on the configuration dialog let you customize the panel widget layout and what data is shown on the panel.
The overview window can be accessed by left-clicking on the panel plugin widget, or from the context menu, similar to the configuration dialog. It shows detailed information for every CPU (core).
This is not a bug, though it might look like one because of the widgets used that pretentiously suggest the user could change something. Changing CPU frequency or the governor is not implemented and probably will never be, as it is supposed to be handled by the kernel or power manager. The only function this plugin nowadays performs is showing CPU frequency information. The CPU info dialog is a remnant of the past when it was still possible to change these settings (or at least when it was planned to implement this). It will be redesigned to use proper widgets in a future version. More information about this can be read in bug #3428.
Bugs should be reported to the Xfce bug tracking system. Before reporting bugs, please look if your issue has not been reported before, has already been solved or is on the TODO list. Also make sure you've read the README. Always make sure you're using the current version.
The normal (and best) way to get this plugin is to use the package manager or port system of your operating system.
If it isn't available there, or if you want a different version, you can download it in source form from http://archive.xfce.org/src/panel-plugins/xfce4-cpufreq-plugin/.