Well, I wouldn't say it would outright not work, but it certainly won't run at full speed if the system boots. The T5550 gets its 1.83GHz speed by multiplying it's "base clock" (FSB/4) by it's multiplier, in this case (667MHz/4)*11=1.83GHz. On a 533 FSB, that gets reduced to (533/4)*11=1.46GHz...