yes you are correct you should set them to 333. it will only run, at maximum, the lowest maximum memory speed supported. example: you have DDR 266, DDR 333, and DDR400 memory installed, they can only run at maximum 266.
to set it to 333 change your CPU external frequency from 133Mhz to 166Mhz in your BIOS.
more info:
http://forums.extremeoverclocking.co...threadid=20942