533/333
as i understand, the p4s333 bios does not support the same pci divisors that the p4s533 does. now you can put a 533 bios on a 333. i'm not well versed in the 533 on a 333 bios arena, but i have read of some people having problems. if you go to asusboards.com, there is a 333 to 533 guide posted there you might be interested in.
you might go to the asus website and follow the sis link on the p4s533 page and read the differences between the 645 and the 645dx chipset. there are some benchmarks somewhere on THG (tomhardwareguide.com). the 645dx does outperform the 645. i don't remember all of the specifics, the memory interface was improved if i remember correctly. the 645 may not have supported ata133, which really doesn't matter unless you're getting a maxtor drive.
while you're on the asus site, just look carefully at the differences between the boards as well.
personally, i don't find the p4s533 to be prohibitively expensive. how much money are you looking at saving by going with the 333???
if it's just a bit more, yet it's a better performer with official support for the 533mhz fsb then why not at least guarantee yourself the future stock upgrade to a cpu in that realm whenever whatever a topend 533 mhz fsb turns out to be?????
20 bucks savings on a motherboard isn't going to buy you much extra hardware anyway.
are you planning to overclock??? if so, you're already likely planning to spend good cash on a good hsf - case fans, etc...then you get tired of the noise...water cooling....
IT'S INSANE!
PEACE!
BdK