I've got a MacBook with a Core 2 Duo CPU. I've got [CoreDuoTemp](http://macbricol.free.fr/coreduotemp/) installed which can show the current speed of the CPU. It appears to always show:

```
Mini : 1.0 GHz
Maxi : 2.0 GHz
Current : 2.0 GHz
```

I believe my laptop would run longer on battery if it were to run at a maximum of 1 GHz. Is there a way to configure this, or is the CPU speed adjustment completely automatic?