Is there any program that can tell you? or you have to open the heatsink no matter what to know?

Also, can the RAM hold you back in your Overclock? I mean, if you use super-cheap RAM can that bring you a strap? like some cheap memory would only let you go to 350mhz FSB but some good memory would let you go to 420mhz, can that happen? is this possible?

Thanks