For those speeds mine worked best at 0.635 for both cpu gtls, as I went higher (480s) the higher gtls worked better up to 0.655 for both. Auto on the NB gtl worked fine for me up to about ~470fsb than I set it to 0.665. 1.24NB is not alot especially with a fan on the heatsink and 1.54 pll is also fine. What vid is this chip?