Currently there are two overclocking issue in NF3 250/250GB/Ultra Chipset ...

1 . External PHY SATA is useless once HTT clock > 240 MHz

Solution : No solution yet ...

2 . HTT clock PLL register is powered by stanby voltage , which means after you power down the system , the HTT clock register will remain the same before power down ... If you use low cpu ratio and high FSB combination , the board may fail to boot in next power up ... Ex : 3400+ cpu OC to 300 * 8 , in the next power up , CPU frequency will be 300 * 11 = 3300 mhz immediately

Solution :

1 . Always clear stanby power good signal to make HTT clock back to 200 mhz in every power up , but some stanby power good keeped funciton can not be used

2 . Always turn off stanby power after you powered down the system

3 . Use Mobile CPU instead of Desktop version

4 . Use Spread Spectrum Register to program HTT clock , which is not stanby powered keeped ... but it will cause other problem ...