I suppose you all know this already, but in Ninja Gaiden III in US/EU, you have limited continues and the game is overall as hard as ever. But the famicom version has you taking ½ damage, infinite continues and there's passwords! I tried it out, and I got to level 6 before I had to start save-stating. That's pretty impressive for me since I'm not that skilled. Or, it's telling of how much easier Ninja Gaiden III is in the japanese version...
Anyway, I was wondering.. people have figured out how to hack Mega Man's password system to make you come to Dr Wily with many E-tanks and lives etc, can that be applied to Ninja Gaiden 3 or Castlevania 3?
after reversing password system from available ROM-image you should know if that is possible or not. There is no other way to do that
I don't know the answer to your question, but I'd like to mention that there is a patch for the English Ninja Gaiden III to restore the Japanese difficulty and passwords. I put the updated roms onto my old NG3 cart and it's awesome now that I can get past the third stage! I still haven't beaten it, much like the first game the end has some tricky platforming that I haven't figured out yet.
I took a quick look into this. The short answer is: there are only seven valid password for Ninja Ryukenden III, one for each "act" in the game. There are no passwords that give you more lives or anything like that.
The long answer is that the password system presents you with four boxes which can each contain one of four possible values. This means there is a total combination of 4 x 4 x 4 x 4 = 256 possible password combinations. (The programming savvy reader, at this point, can probably already guess how the password system works). Each of the four boxes sets a value in ram to a value between 0 and 3 (specifically, the values at 0x05A6 - 0x05A9). When you submit the password, the game shifts the values at these four addresses into a single byte. The resultant byte is then checked against seven hard-coded password bytes, located at 0xAC30 - 0xAC36. If it finds a match, it loads the appropriate level. If it doesn't find a match, you're back at the password screen. The password code starts at or around 0xAB94 (at the CLC opcode).
This game is so awesome, especially on a real old CRT with bright flashing.