Inside the Sonic 2 prototype ROM is a series of lost data that tells about earlier builds. When programming a Sega Genesis/Megadrive game, they used various PCB boards, which allowed the programmers to attach chips.
Whenever a new revision was made, it was burnt onto the chips over the old data on the chips. When doing so, the data was written onto the chip a bit randly, leaving open spots on the chip that it didn't write over. Basicly meaning that whatever data was in these "holes" can still be explored. The following information is a collection of descriptions of some of that leftover data. (Special thanks goes out to Nemesis for allowing me to copy his detailed guide word for word.)
End of compressed ARZ 128x128 block mappings
This small reminant of a rather recent build indicates a minor change in the above blocks of data, which resulted in a slightly shorter file size. This was most likely just a minor amendment to the block mappings for a level, resulting in them not compressing quite as well.
large chunk of CNZ 128x128 block mappings
This contains a large proportion of an earlier version of the CNZ 128x128 bl
This contains a large proportion of an earlier version of the CNZ 128x128 block
mappings. The block of data is missing the first 3340 (D0C) bytes. From this
we can see a massive chanage in CNZ between this compilation and the one in our
beta. These block mappings have been changed so radically, that only a pattern
in thier layout is recogniseable when compared to our current beta one. This
indicates a massive restructuring in the order of the 16x16 block mappings of
this build as well, but unfortunately that data was written over.
CPZ patterns/block mappings
These are the complete patterns and block mappings for an earlier version of CPZ.
There are a few minor changes in the patterns, and some fairly major changes in the
16x16 and 128x128 block mappings.
 leftover data |
 the active data |
Compressed ARZ 128x128 block mappings
This lost data is in an uncompiled form, and at first I mistook it for code. Apart from the fact it is in this form, the data appears to be very close to that of our current beta. There is a commented line at the very start of the block, which contains further information about the block of compressed data. Thanks go out to Iceknight, who figured out that the text in this comment was in Kanji, and thanks go out to Kojichao and sth2k for translating it. The commented line reads:
Before compression $8000 After compression $2c00 Compression ratio 34.4% Cell number 1024I had already guessed the purpose of the first three numbers, But I still can't figure out the puropse of the last one, or at least not one that would be worth putting in a comment. If anyone has any idea what the fourth number is used for, let me know.
Half of SEGA intro sound
This is a large proportion of the sega intro sound from an earlier compilation.
There do seem to be minor differences in the waveform, but for the most part it's
identical to the one in our beta and the final version.
Pattern load cue's
Due to changes in the structure of the rom, there are quite a few pattern load cue's
left from previous compilations. In fact, in this one small area in the rom, I have
identified six different layers of lost data from previous compilations, and these
compilations seem to be a lot newer than the remains of level data judging by some
of the link locations on the cue. Here's a breakdown of the lost pattern load cue's:
| 24804 | End of boss level (unknown boss/unknown boss/small explosion/smoke trail/EHZ boss/unknown) | (?)[5] |
| 24828 | ARZ (lever spring/V spring/H spring) | (?)[1/2+1] |
| 24838 | Title card (title card patterns) | (0) |
| 24840 | End of signpost level (signpost/hidden bonuses/unknown) | (0)[2] |
| 24854 | End of boss level (unknown boss/EHZ boss/unknown/unknown boss/unknown boss/small explosion/smoke trail/EHZ boss/unknown/) | (2)[8] |
| 2488C | End of boss level (smoke trail/EHZ boss/unknown) | (?)[1/2+1] |
| 2489C | MCZ (log/invalid pointer (7976C)/V spring/H spring) | (?)[3] |
| 248B4 | CNZ (invalid pointer (AB748)/invalid pointer (AE75A)) | (1) |
| 248C2 | CNZ (spikes/D spring/V spring/H spring) | (3) |
| 248DC | CPZ (invalid pointer (B1D24)/stuff/striped blocks/unknown/big platform/small platform/spring stopper/water/unknown/stuff) | (9) |
| 2491A | CPZ (spikes/unknown/invalid pointer (7976C)/V spring/H spring) | (4) |
| 2493A | ARZ (invalid pointer (B9686)/water/leaves/arrow shooter/splash) | (4) |
| 2495A | ARZ (spikes/invalid pointer (7976C)/V spring/H spring) | (3) |
| 24974 | Title card (invalid pointer (7E222)) | (0) |
| 2497C | End of signpost level (signpost/invalid pointer (7F37A)/invalid pointer (7F206)) | (2) |
| 24990 | End of boss level (invalid pointer (7C4BC)/invalid pointer (7D942)/invalid pointer (7E12E)/invalid pointer (7C4BC)/invalid pointer (7CBF8)/invalid pointer (7D7DE)/invalid pointer (7D85C)/invalid pointer (7D942)/invalid pointer (7E12E)) | (2)[8] |
| 249C8 | ARZ (invalid pointer (?AD00)/invalid pointer (7976C)/V spring/H spring) | (?)[1/2+2] |
| 249DC | Title card (invalid pointer (7E222)) | (0) |
| 249E4 | End of signpost level (signpost/invalid pointer (7F37A)/invalid pointer (7F206)) | (2) |
| 249F8 | End of boss level (invalid pointer (7C4BC)/invalid pointer (7D924)/invalid pointer (7E12E)/invalid pointer (7C4BC)/invalid pointer (7CBF8)/invalid pointer (7D7DE)/invalid pointer (7D85C)/invalid pointer (7D942)/invalid pointer (7E12E)) | (2)[8] |