It will still function. A motherboard that cannot run RAM at a certain speed will just underclock it. You can adjust RAM speed in the BIOS of most motherboards...there are some OEM boards that do not allow it. Many motherboards can run RAM higher with no issues than the specs actually say.
On my Evga 780i it says DDR2 at 1066MHz is supported. I can run my Corsair at 1200MHz with no issues, very stable.