[Arakon]

the only external mod requires a swaptrick and can't play DVD-R.
a external non-swap mod is simply impossible, the ps2 has no external interface that allows direct BIOS access (which is what is needed for the mods to work), and USB itself is not able AT ALL to take any influence on ANY functions of the ps2 actually. the so-called USB mod doesn't have a thing to do with USB, other than abusing a port and using the power and GND lines from it.