I did a little Everest bandwidth testing. Seems 565 FSB on the 5:6 divider using PL 8 is the max I can stabilize enough to bench, and that took 1.78 vNB. Think this is about as far as X48 and DDR2 can go on air on this setup.

555 FSB / 666 MHz (DDR2-1333 MHz) / PL 8



560 FSB / 672 MHz (DDR2-1344 MHz) / PL 8



565 FSB / 678 MHz (DDR2-1356 MHz) / PL 8