Need help with PS2DIS

(If you wish to skip straight to my PS2DIS situation, go ahead.)

There are two series of games called Dynasty Warriors and Samurai Warriors that are made by Koei. These games are hack-and-slash games, and one or two years after releasing a game, Koei releases an expansion called Xtreme Legends, so the game would be called Dynasty Warriors 5 Xtreme Legends, for example. (This topic is about the PS2 games only.)

If you play those expansion games by themselves, you'll only get the new features (like characters or modes) that were added on the new game, and if you want to play the original game with the new features, you'll have to use a feature called "Import" or "Load Original". If you do, the game will prompt you to open the disc tray, then put in the disc of the original (or non-expansion) game, then finally ask you to put back the disc of the expansion game. Then you'll be able to play the original game with the expansion features.

The thing is, all that the "Import" or "Load Original" modes do is recognize the game ID (SLUS, etc.) of the original game, then allow you to play what was already on the expansion disc. So, in reality, the expansion games contain both the content from the original AND expansion games, but they'll only allow you to play it all if you do a disc recognition procedure first.

Why all this info? If you're playing out of a PS2 that is in fine working conditions, then you're ok, just swap the discs and you can play it all. But for people that are playing with PCSX2, OpenPS2Loader or even a PS2 that is not in 100% working condition, then you're out of luck. PCSX2 doesn't have a open/close disc tray feature, and doesn't support in-game disc-swapping. OpenPS2Loader will freeze at "Please open the disc tray". And if you're one of the people with malfunctioning PS2 consoles like me (mine won't recognize DVD9 games and won't recognize the game's ID), then you won't be able to play the full game + expansion, even if you own both games.

Many threads have been made over the years about disc swapping Dynasty and Samurai Warriors games on those conditions, but most of the answers say it can't be done. I thought I wouldn't be able to play those games like I once had played on my PS2, until I found out a thread about a Japanese hacker who had done it. He made an Action Replay code of the Japanese version of Dynasty Warriors 5 that allowed you to play the game without having to do the disc-swap procedure. And an user at PSX-Scene, lee4, converted the code to the US version, so I was able to use PS2DIS to find out what it does to the game's ELF (I guess that's what it is called), but I am extremely confused. You see, I started to use PS2DIS and even learned some MIPS just to do this.

PS2DIS situation: In Dynasty Warriors 5 Xtreme Legends, if you play without this specific code, you'll play the game like it was just an expansion, and the code will make it so that you'll be able to access the content of both the expansion and the original game (for those who haven't read the paragraphs above, all the content is included in the expansion game disc, it just blocks it until you do a disc swapping procedure). The code provided by lee4 of PSX-Scene is 201ABED4 24020001 (yes just one line), so it modifies the address 001abed4 of the ELF file, and changes its data. Before the code, it looks like this on PS2DIS:

001abed4 8f82868c lw v0, $868c (gp)

and after you change to what the code says, it looks like this:

001abed4 24020001 li v0, $00000001 (__00000001)

(The address 00000001 is empty, if you guys need this info.)

When you patch the game with the code on PS2 Patch Engine, it simply works like magic. The game simply doesn't block any content and you can play both the expansion and the original game with all features.

What I want to do: I want to make similar codes for other Koei games, like Samurai Warriors and Samurai Warriors 2 and their respective expansions. A lot of people want to play these games, and will be sure to post my results.

What I don't know: I have no idea whatsoever of what the code above changed. Does it have to do with the offset $868c? Does that offset represent an address? If so, how do I find that address? Any, and I mean ANY type of clue you guys can give me will be much appreciated, since I don't know what to look for and I don't know what I'm dealing with. If I can find out what the code changed, maybe I could replicate this to other Koei games since they all work the same way.

Thanks in advance,


Obligatory legal part: Yes all of this assumes that the person that enters the code owns both the original games.

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