You wont void warranty by trying to unlock. For unlocking you have to use mobo with SB 710 or Sb 750 with AMD's Advanced Clock Calibration. For good batches, just seting it to Auto might do the trick. For some nasty batches, you have to try individual ACC values ( ranging from +12 to -12) per core to find the most stable position.
Also unlocking is temporary, and is specific only to that boot. So just remember toe ACC values that worked. Just set that in BIOS once and its like an X4 for the rest of the life. But once you reset the BIOS for some reason, you have to fiddle with ACC again. If you put that proccy on another mobo without ACC, its just a plain X2 or X3, as the unlocking was temporary.
But the good thing is, once you find a stable unlocked proccy, it has exactly the same performance of that on a PII X4 clock to clock. On earlier days, there were certain batches called as the "Cherry Batches" which has 100% unlock success rates. That means, if you find those batch proccy on store, its like meeting a guarenteed X4 at X2's price
some of such batches were 0922APMW, 0923CPMW, 0922CPMW etc.
Nowadays the unlock rate has been cut by 1/4 and no suh cherry batches exists or people are lazy to research and find cherry batches as the unlocking thing has gotten old.
PS: i was lucky to have one 0922apmw which i was sure was a cherry, and set ACC auto on very first boot itself. Easily does 4Ghz+ on all cores.