Disassemblies

Disassemblies (also called split disassemblies) are reverse-engineered deconstructions of a game's original ROM, created by translating its compiled machine code back into assembly language. In the context of Sonic the Hedgehog games on the Sega Mega Drive/Genesis and its expansions, disassemblies are community-created projects that aim to reconstruct the original game code in a readable and easily editable form. All 4th generation Sonic games use Motorola 68000 assembly.

These projects allow developers to study how the games work internally, modify their behavior, and rebuild bit-perfect ROMs from source. Over time, many disassemblies have been expanded with labels, comments, bug fixes, and optional improvements, making them a standard foundation for modern Sonic ROM hacking.

This page lists all the public disassemblies made by the Sonic hacking community. Some of these are still actively maintained on the Sonic Retro GitHub account, and they are the most up-to-date and accurate disassemblies. Other disassemblies are only listed here for historical purposes and are usually considered obsolete.

Sonic the Hedgehog (16-bit)

The main Sonic 1 disassemblies all support REV00/REV01/REVXB through the Revison assembler flag. Set to 1 by default.

• Sonic Retro's GitHub account hosts the most up-to-date version of the Sonic 1 disassembly, maintained by the community:
  • AS branch - Default branch, targeting the AS Macro Assembler for cross-platform compatibility and allowing to assemble the Z80 sound driver. Originally ported by MainMemory.
  • ASM68K branch - Original assembler used before the migration to AS, originally named as the "master" branch. It builds much faster than AS, but is only natively compatible with Windows and doesn't support Z80 (the sound driver is instead provided as a precompiled binary blob), as well as lacking various other features of AS.
  • ProjectSonic1TwoEight branch - Special fork of the AS branch, adding MarkeyJester's Project Sonic 1: Two-Eight 128x128 chunk system. Originally ported by Clownacy.
  • All branches are periodically published as stable GitHub releases.
• Hivebrain 2022 - A heavily expanded 2022 version of the classic 2005 disassembly by Hivebrain, featuring various improvements and more thorough documentation. It targets a modified version of ASM68K known as AXM68K for supporting Z80 macros.

Historical Disassemblies

GitHub MainMemory has made a port of the main GitHub branch to AS and added a MapMacros branch that converts all sprite mappings to a macro format. Both of these have since been merged into the main upstream. Kramlat has made a fork of the MapMacros branch targeting the AS assembler, allowing for cross-platform building for Linux and Mac users. Unfinished, and since the inclusion of the MapMacros into the main repository, obsolete. Kramlat has also made a fork of the main branch featuring similar changes as Hivebrain 2022, and targets the AS assembler. Stale since 2023. Kramlat has also made a fork of the Project Sonic 1: Two-Eight branch targeting the AS assembler, allowing for cross-platform building for Linux and Mac users. Obsolete since MapMacros have been merged into the main upstream. SVN Sonic 1 SVN Disassembly (info) (676 kB) - Snapshot taken on 16 July, 2010. Revision 00 Old Hivebrain 2005 disassemblies: Sonic 1 (Split and Text by Hivebrain) (ASM68K) (info) (457 kB) - A modified version of Hivebrain's split disassembly targeting ASM68K. As a result, it builds much faster, does not need to use an external program for includes (and hence bypasses s1comb.asm), and can be optimized in various ways. The ASM68K branch of the GitHub version of the Sonic 1 disassembly is based on this version. Sonic 1 (Split and Text by Hivebrain) (AS) (info) (1,008 kB) - A modified version of Hivebrain's split disassembly targeting AS. As a result, it does not need to use an external program for includes (and hence bypasses s1comb.asm), and AS-specific features such as functions, nameless temporary labels and improved macro facilities can be used. The GitHub version of the Sonic 1 disassembly is currently based on this version. Build tools for building on non-Windows platforms are available here for Linux and here for Mac. Sonic 1 (Split and Text by Hivebrain) (info) (771 kB) - The original June 2005 release of Hivebrain's Sonic 1 split disassembly. SonED2 project files are available here. It targets SNASM68k. Very well labeled, but because of certain problems with SNASM68k it is recommended to use either the ASM68k version or the AS version of this disassembly (also note that this version doesn't work with any 64-bit OS!). Old drx disassemblies: Sonic 1 (IDB by drx) (info) (1.14 MB) - The very first Sonic 1 disassembly, by drx. This is an IDB file and can only be opened in IDA Pro. Sonic 1 (Text Format by drx) (info) (673 kB) - The very first Sonic 1 disassembly, by drx. This is in text format and can be opened in any editor. It targets SNASM68k. Revision 01 Sonic 1 REV01 (Split Format by Esrael) (info) (576 kB) - A disassembly of Sonic 1 revision 1 released in 2009 by Esrael. It targets SNASM68k. Other Project Sonic 1: Two-Eight (by MarkeyJester) - Modifies the game's level layout engine to use Sonic 2's 128x128-pixel chunks and path-swapping system. Sonic 1 Z80 Sound Driver (Split+Text format by Puto) (info) (1.2 MB) - A disassembly of the Z80 portion of the Sonic 1 sound driver. It targets the Macro Assembler AS, and is cross-platform. Sonic 1 Z80 Sound Driver (Text format by Flamewing) (info) (1.05 MB) - A vastly improved version of Puto's disassembly of the Z80 sound driver.

Sonic the Hedgehog 2 (8-bit)

• Sonic 2 Master System (Split format by Glitch) ^(info) (1.18 MB) - A split disassembly of the Master System version of Sonic the Hedgehog 2 (8-bit), by Glitch. This disassembly has been uploaded to GitHub and is available here.

Sonic the Hedgehog 2 (16-bit)

Final

The main Sonic 2 disassemblies all support REV00/REV01/REV02 through the gameRevision assembler flag. Set to 1 by default.

• Sonic Retro's GitHub account hosts the most up-to-date version of the Sonic 2 disassembly, maintained by the community:
  • Master branch - Default branch, targeting the AS Macro Assembler for cross-platform compatibility and allowing to assemble the Z80 sound driver.
  • Mega Play branch - A disassembly of the Mega Play version of Sonic 2, by Clownacy.
  • Sonic Classics branch - A fork of the Master branch that includes changes from the Sonic Classics/Sonic Compilation version of Sonic 2, by Clownacy.
  • Beta 8 branch - A disassembly of Sonic 2 Beta 8, by Clownacy.
  • Knuckles in Sonic 2 branch - A disassembly of Knuckles in Sonic 2, by Clownacy.

Historical Disassemblies

GitHub MapMacros branch - A fork of the Master branch by MainMemory that converts all sprite mappings to a macro format, which has since been merged into the main upstream (although unlike the Sonic 1 disassembly, the branch itself was not deleted). Revision 00 Sonic 2 Rev 00 (Text Format by drx) (info) (1.31 MB) - A disassembly of Sonic the Hedgehog 2 revision 00, by drx. It targets SNASM68k. Revision 01 Sonic 2 (Split and Text by Xenowhirl) (info) (2.5 MB) - The 2007 release of the disassembly of Sonic the Hedgehog 2, by Xenowhirl. It is far better labeled than its predecessors and the assembly times are very fast (1-5 seconds). The disassembly itself is fully SonED2 compatible, and project files are bundled. It targets the Macro Assembler AS, and is cross-platform. The GitHub version of the Sonic 2 disassembly is based on this version. Tools for building for Linux are available here and Mac users should click here for build tools. Sonic 2 (Split and Text by Aurochs) (info) (1.15 MB) - The 2006 release of the disassembly of Sonic the Hedgehog 2, by Aurochs. It is better labeled than Nemesis' disassembly and the compile times are much faster. The disassembly itself is fully SonED2 compatible, and project files are bundled. It targets the Macro Assembler AS, and is cross-platform. Old Nemesis disassemblies: Sonic 2 (IDB by Nemesis) (info) (2.24 MB) - A disassembly of Sonic the Hedgehog 2, by Nemesis. This is an IDB file and can only be opened in IDA Pro. Sonic 2 (Text Format by Nemesis) (info) (1.31 MB) - A disassembly of Sonic the Hedgehog 2, by Nemesis. This is in text format and can be opened in any editor. It targets SNASM68k. Sonic 2 (Split Format by Nemesis) (info) (793 kB) - Nemesis's Sonic 2 split disassembly, targeting SNASM68k. This disassembly is rather slow to rebuild due to the use of an external program (combine.exe) to insert binary files into the ROM - the following two disassemblies work around this by using incbins instead of combine.exe: Sonic 2 (Text Format with Incbin by shobiz) (info) (375 kB) - A drop-in replacement for the s2.asm file in Nemesis' Sonic 2 split disassembly, by shobiz. This disassembly uses incbins to greatly speed up compile times. It is also fully SonED2 compatible without requiring any modifications. This disassembly targets SNASM68k. Sonic 2 (Text Format with Incbin by Xenowhirl) (info) (362 kB) - Identical to shobiz's modified disassembly, but does not work on later Windows versions due to the differences in the way those operating systems handle 8.3 short filenames. Revision 02 Sonic 2 revision 2 (Split Format by Esrael) (info) (1.06 MB) - A disassembly of Sonic 2 revision 2 released in 2012 by Esrael. It targets SNASM68k.

Nick Arcade prototype

• Sonic 2 Early Prototype (Split Format by Super Egg) - A split disassembly of the Sonic the Hedgehog 2 Nick Arcade Prototype by Super Egg, targeting ASM68K.

Historical Disassemblies

Old drx disassemblies: Sonic 2 Early Prototype (IDB by drx) (info) (1.38 MB) - A disassembly of the Sonic the Hedgehog 2 Nick Arcade Prototype, by drx. This is an IDB file and can only be opened in IDA Pro. Sonic 2 Early Prototype (Text Format by drx) (info) (886 kB) - A disassembly of the Sonic the Hedgehog 2 Nick Arcade Prototype, by drx. This is in text format and can be opened in any editor. It targets SNASM68k.

Simon Wai prototype

• Sonic 2 Beta (Split Format by Alex Field) - A split disassembly of the Sonic 2 Simon Wai Prototype, by Alex Field, targeting the AS Macro Assembler for cross-platform compatibility. Based on Esrael's disassembly, it aims to be more in line with the GitHub disassembly of the final game in terms of formatting, such as using its label and variable names. It also comes pre-packaged with SonLVL project files.

Historical Disassemblies
Sonic 2 Beta (Split Format by Esrael) (info) (832 kB) - A disassembly of the Sonic 2 Simon Wai Prototype, by Esrael. It targets SNASM68k. Sonic 2 Beta (Split Format by Super Egg) (info) (2.11 MB) - An updated version of Esrael's disassembly by Super Egg and Nayr T'nargh.

August 21, 1992 "Alpha" prototype

• Sonic 2 August 21, 1992 prototype (Split Format by Esrael) - A split disassembly of the Sonic the Hedgehog 2 (alpha), by Esrael. It targets SNASM68k.
• Sonic 2 August 21, 1992 prototype (Split Format by Nyper Yuhgard) - A revised version of Esrael's Sonic 2 August 21 disassembly by Nyper Yuhgard, targeting ASM68k.

September 14, 1992 "Pre-Beta" prototype

• Sonic 2 September 14, 1992 prototype (Split Format by Esrael) - A split disassembly of the Sonic the Hedgehog 2 (pre-beta), by Esrael. It targets SNASM68k.
• Sonic 2 September 14, 1992 prototype (Split Format by Nyper Yuhgard) - A revised version of Esrael's Sonic 2 September 14 disassembly by Nyper Yuhgard, targeting ASM68k.

Beta 4

• Sonic 2 Beta 4 (Split format by Esrael) ^(info) (1.12 MB) - A split disassembly of Sonic the Hedgehog 2 Beta 4, by Esrael. It targets SNASM68k.
• Sonic 2 Beta 4 (Split format by Puto) ^(info) (1.12 MB) - A revised version of Esrael's Sonic 2 Beta 4 disassembly by Puto. Edits include IDA-like formatting and support for ASM68K.

Beta 8

• The GitHub version has a branch that allows for a complete building of Sonic 2 Beta 8.

Knuckles in Sonic 2

• The GitHub version has a branch that allows for a complete building of Knuckles in Sonic 2.

Historical Disassemblies
Knuckles in Sonic 2 (Text & IDA Format by Puto) - A disassembly of the Knuckles in Sonic 2 UPMEM by Puto. This disassembly has been uploaded to GitHub. Knuckles in Sonic 2 (Text & IDA Format by Nyper Yuhgard) - A disassembly of the Knuckles in Sonic 2 UPMEM by Nyper Yuhgard.

Sonic the Hedgehog CD

• The GitHub version is the most up to date version, and supports Japanese, European, and American releases. However, it currently does not support all levels.

Sonic the Hedgehog 3

Final

• The GitHub version of the Sonic & Knuckles disassembly allows building a complete version of Sonic 3, and is the most up to date version.

November 3, 1993 prototype

• Sonic 3 November 3, 1993 prototype (Split Format by Esrael) - A split disassembly of the Sonic the Hedgehog 3 (prototype; 1993-11-03), by Esrael. It targets SNASM68k.
• Sonic 3 November 3, 1993 prototype (Split Format by Nyper Yuhgard) - A revised version of Esrael's Sonic 3 November 3, 1993 prototype by Nyper Yuhgard with help from MarkeyJester, targeting ASM68k.

Sonic & Knuckles

• Sonic Retro's GitHub account hosts the most up-to-date version of the Sonic & Knuckles disassembly, maintained by the community:
  • Master branch - Default branch, targeting the AS Macro Assembler for cross-platform compatibility and allowing to assemble the Z80 sound driver.

Historical Disassemblies

Sonic & Knuckles (Split Format by jman2050) A split disassembly of Sonic & Knuckles created by jman2050 and a variety of other contributors, using Stealth's disassembly. The GitHub version is based on this disassembly. Sonic & Knuckles (IDB by Stealth) (info) (2.4 MB) - The first complete Sonic & Knuckles disassembly, by Stealth. Includes support for Sonic 3 lock-on. This is an IDB file and can only be opened in IDA Pro. Sonic & Knuckles (Text Format by Puto) (info) (2.41 MB) - A text file exported by Puto from Stealth's Sonic & Knuckles disassembly for those who do not have IDA Pro. Tools for assembling (provided by snkenjoi) are available here.

Sonic 3 & Knuckles

• The GitHub version of the Sonic & Knuckles disassembly allows building a complete version of Sonic 3 & Knuckles, and is the most up to date version.

Historical Disassemblies
Sonic 3 & Knuckles (Split Format by Hayate) (info) (3.22 MB) - An IDA export of Puto's Sonic 3 & Knuckles disassembly ran through a couple of Python scripts by Hayate.

Knuckles' Chaotix

Final

• The GitHub version is the most up to date version.

Sonic Crackers

• Sonic Crackers (Split Format by MarkeyJester) ^(info) (530 kB) - A split disassembly of Sonic Crackers by MarkeyJester.
• Sonic Crackers (IDB by Stealth) ^(info) (637 kB) - A Sonic Crackers disassembly by Stealth. This is an IDB file and can only be opened in IDA Pro.
• Sonic Crackers (Text Format by Shobiz) ^(info) (966 kB) - A text file exported by shobiz from Stealth's Sonic Crackers disassembly for those who do not have IDA Pro.

Sonic 3D: Flickies' Island

• Sonic 3D: Flickies' Island disassembly (IDB/Text by Sik) - Hybrid IDB and text split of the Mega Drive version of Sonic 3D: Flickies' Island by Sik. Can only be opened in IDA Pro.

Sonic Spinball

• Sonic Spinball disassembly (IDB by andlabs) - A Sonic Spinball disassembly by Andlabs. This is an IDB file and can only be opened by IDA Pro.