In my research to better understand the differences between the m-chips and the desktop chips, and how the m-chips work on desktop boards, I've dug up some interesting info.
Intel states that the max v-core for the m-chips is 1.75v at any pin. This is off the datasheet and doesn't mean everyone should go cranking their P4's up. But it does make me feel better about running mine at 1.6xv. Also, it say's that extended exposure to the max ratings may affect device reliability (duh!!).
The max temp for the die junction (hottest location on die) is 100c. The chip will automatically shutdown when the silicon reaches 135c, but I haven't found anything yet on temp throttling...
I've also found the pins that control the output voltage (which would go to the mobo to let it know what voltage the chip is running at), and how they're control, but don't know if those states are initially on or off. I'm just gathering info on this right now, I don't intend on doing any modding at this time.