Well, I was going to first do it on a Pentium 4 for laptop, with RMClock, but it wouldn't work because it doesn't support P-state transitions. "Intel(R) SpeedStep(tm) technology and the "old" vision of Enhanced Intel(R) SpeedStep(tm) technology found in mobile Pentium III-M and mobile Pentium 4 processors are not supported."
I then proceeded to try doing it on my Core i7 720QM 64 bit laptop with RMClock, but it wouldn't allow me to because 64 bit isn't supported under RMClock, and RMClock doesn't support Core i series CPU's (the program is getting old). I have another Core 2 Duo laptop that I have been meaning to undervolt when I have the time, which has a supported CPU and is 32 bit.
Following CPU's are supported:
AMD Athlon 64/FX/X2, Sempron, Turion 64/X2, mobile Athlon 64, Opteron and Dual-Core Opteron featuring AMD Cool`n'Quiet(tm) technology.
Mobile or Low-Power Desktop AMD Athlon XP featuring AMD PowerNow!(tm) technology.
Intel Pentium M, Intel Core Solo and Core Duo, Intel Core 2 Duo, Core 2 Quad and Core 2 Extreme, Intel Xeon (Woodcrest and Clovertown cores) featuring Enhanced Intel(R) SpeedStep(tm) technology (EIST).
Intel Pentium 4 600 series (Prescott N0 core), Intel Xeon (Nocona, Cranford, Irwindale, Potomac, Paxville and Dempsey cores), Intel Pentium D 800/900 series (Presler core), Intel Pentium Extreme Edition (Smithfield, Presler and Cedar Mill cores) featuring Enhanced Intel(R) SpeedStep(tm) technology (also known as Demand-Based Switching).
Its safe, and in no way does it reduce speed or anything like that. I'll quite the reason as to why undervolting is done. "Not all processor chips are built equally. Each individual processor have different voltage tolerances. Instead of Intel tuning each chip's voltage individually for the lowest voltage possible and risking instability, they made a fully stable standard voltage for all chips to run on. The problem is this standard factory voltage they put is quite high. Undervolting takes advantage of this by reducing it to the right amount." I got this quote off 'The Undervolting Guide'.