All TbredB are unlocked, and with XP2400+ and up you're guaranteed TbredB. However there are some dumb-a$$ mobos which can have problem with the higher multipliers which these new chips come equipped with. To overcome this simply connect the last L3 bridge with a U of some conductive ink etc (defogger kit). This will shift it from the high multipliers (13x-21.5x) to the low ones (5.5x through 12.5x) and allow these few dumb-a$$ mobos to alter to a lower multiplier thus enabling the higher FSB speeds. Wise words from a good friend of mine, "All CPUs with default multipliers of 13X or higher use 5 bits to set the FID. Most KT400 boards and most nForce2 boards have all five bits for FID. Boards with only 4 FID pins will need you to cross the last L3 bridge."