Inspiron CPU Speed Stepping

I have a Dell Inspiron 6000 with the Pentium M Processor at 2GHZ.

 

I also have a utility that shows the current CPU speed as well as the Fan speed.  It also allows you to control the fan.  In this utility, I noticed that for several weeks, whether my notebook was plugged into AC or running on battery, it was running at 800 mhz, but would clock up to 2GHZ if it was necessary.  This was nice, because my computer stayed a lot cooler.  However, it's now just running at 2GHZ constantly.  Is there a setting for this, or did I/am I experiencing a 'glitch'.

 

Thanks