If the board support DDR2 800, for example, and you put in DDR2 533 it works. It supports lower speeds and higher if you set it manually. For example I had a GA-P965 that was DDR2 800 and I ram my ram at DDR2 1000. If the board can handle it that is.
When mixed with higher speed RAM it will clock both at the lowest speed unless set manually. DDR2 1066 and DDR3 1066 are not compatible as far as I know. Might be a specialty board that can do it.
When mixed with higher speed RAM it will clock both at the lowest speed unless set manually. DDR2 1066 and DDR3 1066 are not compatible as far as I know. Might be a specialty board that can do it.