TUA266 MOB,Which one 256 or 512 Taulatin?

I was thinking of upgrading to a PIII taulatin.My question is,does anyone know if I need the 256 or the 512 chip for my MOB?Will they both work?Does anyone have this board and chip? I just cant find the info I need.Anyone could lend a hand I would greatly appreciate it.
Thanks....

Both will work on Ali Chipset.
As I know, Tualatin 256 doesn't support dual mode.

Thanks for the info.