|It probably depends on what the manual means by 'support'. If it means the motherboard ram frequency can go up to 533 mhz then 667 sticks should work OK as ram can be underclocked to a certain point. If it means they've researched it and found that 533 mhz sticks are the highest rated sticks that can be underclocked to whatever the motherboard supplies then they won't work.|
Very likely it's the former and they should work OK, assuming the board can handle the capacity OK. In any event it shouldn't hurt to try them.