Well BIOS = Basic Input Output System, IOS perform a similar function. Like say you installed a faster CPU than your BIOs could recognize on your PC; if there's an updated BIOS, it may recognize the CPU. IOS is still the same idea, but may have additional functions with a newer revision of a given IOS.
Originally Posted by madmarty
And it's the only current sanctioned downgrade guide we support (designed as Odd stated only for hardmodders @ 4.2 who need out of region support). It can be found here. It still uses softmodding of a kind in order to solve the issues presented by 4.2, of course.
Originally Posted by oddgriffin