As I understand it, the JZ4740 is made to run at a speed between 200 and 400MHz, so it should be perfectly safe to run it at 400MHz, however it could be that the Dingoo A320 itself has not been designed for speeds above 333MHz. Recent firmware seems to always clock back to this speed when you enter the menu.
Any opinions on this? Or, even better, facts? Doesn't the integrated video player overclock to 400MHz as well for example?
Alekmaul: I will be adding my code here tonight. I am at work now and can't access the code from here.