Well, not having done it myself...I do know the general idea.
When you get your shiny new amd chip (athlon-duron) it will be "multiplier locked" which means that it has a "set" multiplier like 7 and the bus speed of your motherboard runs at 100mhz....so using simple math you get 700mhz e.g. 7x100=700
and to "unlock" the AMD chip you have to bridge a few connections on the chip, usualy done with a special pen that has electrical properties...and once unlocked you can set it to 8x or 9x or even a lower number..and the math still works the same...8x100=800mhz and so on. this is as simple as I can make the explanation.
I hope it is enough to help you understand.
BTW, all intel proc's are multiplier locked, and nobody so far has figured out how to unlock them...but AMD's I understand are as easy as pie.
Cheers, Doc