Would it be easy to hack the Megadrive version of Prince of Persia to play properly on a Genesis? (when I mean properly - i'm talking about the speed issues of the music and gameplay between the PAL/NTSC stuff)
Great idea. I've had a short look at this, but sadly it looks like a tough job.
As you've mentioned Prince of Persia PAL is apparently a fully optimized PAL game: Gameplay speed at 50Hz is equal to the NTSC version at 60Hz. Music speed also sounds correct at at 50Hz.
I did something similar for the The Chaos Engine, but that was only a partially PAL optimized game and allowed easy manipulation of music speed.
From what I understand this Prince of Persia optimization would requires 3 steps:
1) Make the PAL game run on NTSC hardware: Easy, can be done by modifying game data based on an action replay/game genie code ( Game Genie Region Bypass Guide by CVGuile on GameFAQs)
Tried this, and it worked.
2) Make the music run slower: according to segaretro.org this game uses GEMS sound driver. GEMS doesn't seem to control music speed via a variable (games like Alien Soldier, GODS, Shinobi 3 do). Music speed in GEMS driver games apparently isn't controlled by a variable; the whole music tracks are different data in the PAL and NTSC versions of optimized games.
I've confirmed this by copy&pasteing the music data from Aladdin NTSC into Aladdin PAL. Music was too slow at 50Hz, and correct at 60Hz. So music tracks have to be completely rewritten to play correclty at 60Hz. There is no NTSC version with "correct" music speed out there, so no way to copy & paste this over. Maybe needs to be rewritten by somebody that truely understands GEMS.
3) Make the game run "too slow at 50Hz, so it runs correctly at 60Hz" .... no idea how to do this in an easy way to be honest.