PUGSY...L@@K - STAGE SELECT - DOUBLE DRAGON II: THE REVENGE

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mU$!c
Posts: 17
Joined: Fri Sep 12, 2014 3:10 pm

PUGSY...L@@K - STAGE SELECT - DOUBLE DRAGON II: THE REVENGE

Post by mU$!c »

[ddragon2u] Double Dragon II - The Revenge (US)

I've been working on this for just a few days now and I already have found some weird stuff just searching for a method to skip stages. Apparently, this task is a challenge, which is why I took it on in the first place.

I have played almost every version of Double Dragon from the 1980's and 1990's and there was never a stage select code left behind in games by the programmers. Never was a Game Genie code that allowed stage select....Not for NES, Super NES, Sega Master System, or Sega Genesis. Infact, I have never witnessed the existence of stage select in any console port of Double Dragon. I think that Double Dragon is coded in such a way that all of the first 3 Missions seem to all be one big level. Just an observation. I think it would be easier to find a stage select code in the console versions than the arcade version.

Is it just me, or is the architecture of this game not allowing level select to each mission? I can skip to the final Stage (aka mission 4) easily, no delay..easy as pie. I can't seem to come up with a code that will allow me to begin the game at stage 2 or 3. I have been trying to figure out how the main CPU handles the data for transitioning to the next stage also. This is what i have below so far.



I seem to have the correct address and variables for mission 2 and mission 3. When I use those variables, I start on level 2 or 3. I can hear the music, I can see the statistics (Pow/time/ credits..etc.), but the level is not there...black background. Billy dies automatically, falls off of the screen, disappears off-screen, you see the continue countdown, and then game over.

Image

UPDATE: I made a few edits to the code. I discovered in these 80's games the corresponding memory addresses that store data for each level have linear variables. Upon taking another look playing through the game, the levels are very long, so not a mission 5 in this game, only 4 missions like the original Double Dragon (Double Dragon I). Double Dragon II is basically an upgrade of Double Dragon I, just that simple. I have been taking a look at how The Sega Genesis port of Double Dragon I handles the memory location for stage data, as it handles the data the same way, but the addresses are in different locations is all, same variables except in 16-bit. Obviously, I will be looking at Double Dragon II: The Revenge (J) for Sega Megadrive. I have Game Genie Codes for the Sega Genesis (UE) port of DDI (tested and kicking like Jackie Chan). These are ROM writes.

Double Dragon I (UE) [Sega Genesis]

Constantly writes 1 to the ROM address 0x492.

Code: Select all

AECA-AAEW = 000492:0001 = Start on Mission 2
Constantly writes 2 to the ROM address 0x492.

Code: Select all

AJCA-AAEW = 000492:0002 = Start on Mission 3
Constantly writes 3 to the ROM address 0x492.

Code: Select all

ANCA-AAEW = 000492:0003 = Start on Mission 4
So, I'm on to something here...gonna test and see if more beautiful code comes from this :)


[ddragon2u] Double Dragon II - The Revenge (US)

Code: Select all

<cheat desc="Stage Select"> <comment>Only works for Mission 4 currently.</comment>
    <parameter>
      <item value="0x00">1</item>
      <item value="0x01">2</item>
      <item value="0x02">3</item>
      <item value="0x03">4</item>
    </parameter>
    <script state="run">
      <action>maincpu.pb@0036=param</action>
    </script>
  </cheat>

Got any ideas, Pugsy?

Anyway, if anyone finds some addresses and variables that would be helpful in this endeavor, please feel free to post here or PM me. However we get it done is fine by me, peeps.


What ya got for us Pugsy? :)
Last edited by mU$!c on Tue Jan 27, 2015 12:55 pm, edited 15 times in total.
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Re: PUGSY...L@@K - STAGE SELECT - DOUBLE DRAGON II: THE REVE

Post by Pugsy »

It certainly isn't straightforward, I've spent a few hours looking at it and the memory paging really screwed up my investigation. Nothing meaningful to report...though I did find a 16 bit value that allows you to move through a level but that was kind of screwy as well.
Pugsy

Servicing your cheating needs since 1985 8)

Grab the latest cheat collection:
MAME 0.259 XML cheat collection (6 OCTOBER 2023) from http://www.mamecheat.co.uk or direct from:-
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mU$!c
Posts: 17
Joined: Fri Sep 12, 2014 3:10 pm

Re: PUGSY...L@@K - STAGE SELECT - DOUBLE DRAGON II: THE REVE

Post by mU$!c »

Pugsy wrote:It certainly isn't straightforward, I've spent a few hours looking at it and the memory paging really screwed up my investigation. Nothing meaningful to report...though I did find a 16 bit value that allows you to move through a level but that was kind of screwy as well.
So sometime that 16-bit value allows you to pass on to the next level, but sometimes you repeat the same level or black screen?

what is the address of this value? same? 0036?
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