basically, it's best to overclock with no divider, as your RAM will run faster. But if your RAM can't take it, then you have to use a divider to stay stable. with DDR500 RAM you basically pay for a garuntee that you can overclock to a fsb of at least 250 before needing to use a divider. As long as it's not DDR2. DDR2 is not compatible with DDR1 motherboards. remember that the FSBx2 gets your DDR speed since DDR is double data rate. As far as the 1GHz, that comes from the HTTLink (Hyper Transport link) you get that from the FSBxHTTLink. If the FSB is 200 and the HTTlink is at 5x, your total HT FSB is 1Ghz. I think for NF4 boards, 1ghz is the maximum stable unless you increase the northbridge voltage, which the performance gains are hardly worth the risk. Crossfire boards supposedly can go beyond 1GHZ without breaking a sweat.