Sonic 2 (Aug 21, 1992) Disassembly

Discussion in 'Engineering & Reverse Engineering' started by Esrael, Feb 2, 2020.

  1. Esrael

    Esrael

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    Neto Assembler Editor / Sonic 2 Delta / Neto MD-DOS
    This disassembly was gerenated with use of "Neto Assembler Editor v0.14a"

    Sonic 2 Beta (rev. 21/08/1992) disassembly

    You can view all levels of this beta in "Neto Assembler Editor".
    Run "Neto Assembler Editor" and then Click in Tools -> Sonic Series Level Layout Editor and Load File "S2210892.epr"

    Neto Assembler Editor v0.14a

    This version has a lot of unlinked data which are at the same location of the Sonic 2 Beta (aka Simon Way version).
    Some enemies from Sky Chase like Balkiry, Clucker, Nebula and Turtloid have the object code and art data added.

    This version implements object code for the Blink, Bubble Monster and the Spinning ball enemies.

    If you want to see these enemies working, I have linked them to Casino Night in Debug Mode, just run Casino Night with Debug Mode Activated and then place the selected object.
    Download the modified ROM with these enemies enabled:
    Sonic 2 Beta - Lost Enemies Enabled


    Enjoy!

    Best regards.
    ------------------
    Neto
     
    Last edited: Feb 2, 2020
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  2. Travelsonic

    Travelsonic

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    Interesting to see Sky Chase badnik art and object code implemented at this point n development.
     
  3. Billy

    Billy

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    Excellent work!
     
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  4. evilhamwizard

    evilhamwizard

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    [​IMG]
    These are some bouncy bois

    [​IMG]
    *plop*

    [​IMG]
    *pop*

    Very awesome work! :)

    Were you able to get the bosses for Chemical Plant and Oil Ocean loaded by any chance?​
     
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  5. Wow, I never thought I would see these objects in action.

    This is fantastic.
     
  6. It's absolutely incredible to see these objects actually alive!
     
  7. Overlord

    Overlord

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    Oh wow, that's really something from what we already knew about those things. Great work Esrael!
     
  8. Hez

    Hez

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    So not diving into this at all myself, and with pure speculation, does this leftover code show up in any other builds? I ask because I almost feel like (well, know) they reuse these cartridges quite often to save costs. With that being said, I ALSO feel like they frequently built different versions of the game to test features.

    Basically what I'm saying, is that the team tasked to do badnik coding may have been handed this particular cartridge to test on hardware. The time came to build a stable version to send to a magazine company, so they nabbed it and wrote the game on it. The leftover data from the badnik coding teams build is left in places.

    Theoretically -- other builds could contain completely different data completely in these blank/dark spots?
     
  9. Diablohead

    Diablohead

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    Seeing those balls bounce around like that, really cool.
     
  10. drx

    drx

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    :rolleyes:
    That’s not how EPROMs work. When you erase an EPROM, it erases the entire chip. There are no leftovers that get overwritten, it’s a fresh ROM every time.

    Leftovers happen when instead of padding with 00s, ROM segments get padded with garbage/leftover RAM data in the assembler/linker.

    I haven’t looked at these, but some leftovers are also just code/data that isn’t referenced anywhere, but still part of the same build.
     
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