I see that I'm not the only one who experienced the undocumented cpu throttling 'feature' in the older Ma
Anyway, it's not exactly a fixed factor of 2. I owned a while MacBook that was powered by Intel's Napa (refresh) platform (that's even before Santa Rosa!) and had a processor clocked at 1.83GHz. When the battery is removed and the notebook powered solely on AC, the frequency dropped to 1.0GHz.