First off, the motherboard of the 450 will only be able to operate at 100 mhz bus (unlikely you'd be able to overclock bus all the way to 133). That said, I think one of two things will happen. Either you'll plug in the processor, a it simply won't work. Or, you'll plug it in, and it will apply the 100 mhz bus and some multiplier to get the 533 to operate at a slower speed.