I think he means undervolting. If so, you can't really say for sure. You just have to play around with the voltages. Some can undervolt better than others because of the way the chips are manufactured. Underclocking is a different thing. Underclocking is done automatically on Pentium M's by the motherboard (I believe). 2.0Ghz, automatically underclocks to 800Mhz, I believe. You can set it lower manually by using Centrino Hardware Control or RMClock.