unlocking the CPU and changing the multiplier are two entirely different things.
No motherboard can unlock a Duron or Tbird on it's own, as said above, the L1 bridges have to be connected with a pencil or condictive paint pen or other condictive implement. If your CPU is locked (as most are when they come straight from the factory) no amount of jumpers, dip switches, bios settings, or banging your head on you case will unlock it.
Once you have unlocked your CPU, if your motherboard has dips, jumpers or bios settings to switch the CPU parameters (FSB, multiplier, voltage)
you SHOULD be able to manipulate these to overclock. Motherboards that can manipulate these parameters:
FIC AZ11E
Abit KT7 and its various iterations
Asus A7V and iterations
MSI K7T Pro 2A
Iwill KK266
Other boards may be able to change settings but none that I have heard of.
Sickboy