On certain CPUs and with some operating systems, speeds and voltages are sometimes not detected or adjusted properly.
Example: on my family's PC, with Athlon 64 3500+ and XP X64, the speed was not adjusted until I added the /pmtimer switch to boot.ini. Without that, RMClock couldn't do a thing.
When I resume from standby on my laptop, the speed is shown as higher than it is (I can't recall the exact number as it's been a while, I don't use standby often, but it's the same all over, i.e. the slowest speed is shown, for example, .5GHz higher and so is the highest).
It's best to see if anyone else has used it successfully with your specific CPU if it's new before expecting it to work.
Having said that, there aren't many completely issue-free programs out there, so don't let it put you off - it's worth a shot if you want to lower the heat output of your PC and/or save battery power.