questions about DVFS in saving energy

[kch670 at eecs.northwestern.edu (Kai Chen)]

Hi, could anyone here have some idea of the following questions about
Dynamic Voltage/Frequency Scaling techniques used for energy
efficiency, or please give a pointer that I can trace,
1) how many servers in the market support this technique?
2) how many voltages/frequencies can the servers support?
3) What?s the transition time and cost (power) between these
voltages/frequencies?

Thanks,
-Kai