Interesting question, since these are 133mhz FSB chips underclocking them at 100 FSB for a KT133 chipset should be possible except one question is unanswered. Will you be able to unlock them? These are different chips from the Thunderbirds, updated core, lower voltages. Does anyone know if the bridges are the same and if they are unlockable or even if they are locked? So I cannot answer your question.