which rom do you use?I clocked to 787 MHz with settings
boottime 90000
checktime 17
command 0
performancelevel 38
screenoffperformancelevel 1
settlingtime 10
or you can clock not more than 714 but stable(standart speed is 604MHz)
boottime 90000
checktime 20
command 0
performancelevel 1
screenoffperformancelevel 44
settlingtime 10