Very strange behaviour indeed, interesting settings on that MB are around FSB hole so we are getting mad as it's not easy to determine if we are right inside or not. Another strange thing on my MIIF is that even unstable at 500 FSB I'm still booting at PL8, but at 515 I cannot even use PL9, only PL10...I have to investigate values such as 505/510 to see if I have chance to boot at PL9 or if it goes straight from PL8 to PL10.