Sonic Drift

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Bellow are some notes for Sonic Drift. These notes are based on Ravenfreak's research.

Error Handler

This game has a hidden error handler text located at offset $46350. Whenever the game crashes it will display this error text before returning to the Sega screen. The error handler routine is located at offset $462CF.


It should be noted that this is the only 8-bit Sonic title to utilize battery back up. The game keeps track of the player's best times in Free Run Mode. The SRAM read/write code is located at offset $8F5 in the ROM.

Object Pointers

Offset Description
$70AA Ring
$70AD Palm Tree Left
$70B0 Palm Tree Right
$70B3 Stone Pillar Left
$70B6 Stone Pillar Right
$70B9 Spring Yard Block Left
$70BC Spring Yard Block Right
$70BF Labyrinth Block Left
$70C2 Labyrinth Block Right
$70C5 Lamppost Left
$70C8 Lamppost Right
$70CB Electrical Sphere Left
$70CE Electrical Sphere Right
$70D1 Booster
$70D4 Invincible Power Up
$70D7 Spring
$70DA Spike Ball
$70DD Heart
$70E0 Sign Left
$70E3 Sign Right


All art in the ROM can be edited in Aspect Edit. The player sprites are uncompressed and each sprite consits of 9 tiles that make up a 3x3 grid. The following diagram shows the tile rearrangement data for their sprites:

[1] [2] [3]  
[4] [5] [6]
[7] [8] [9]

Each map in the game consists of 80 tiles that make up a 8x10 grid. The tile arrangement is as follows:

[1] [2] [3] [4] [5] [6] [7] [8] [9] [10]

Level background sprites are compressed. However, the title arrangement is different than the maps. Further research is needed to fully understand the tile arrangement data at this time.

Art Offsets

Offset Description
$87E7-$9436 Small Text Sprites (Compressed)
$9B3F Marble Red Map (Compressed)
$A1FA Spring Yard Red Map (Compressed)
$A954 Labyrinth Red Map (Compressed)
$B072 Star Light Red Map (Compressed)
$B74F Scrap Brain Red Map (Compressed)
$D33C Spring Yard Block (Compressed)
$D4B9 Labyrinth Block (Compressed)
$D63F Star Light Lamppost (Compressed)
$D724 Scrap Brain Electric Orb (Compressed)
$D882 Green Hill Green Map (Compressed)
$DFA1 Marble Green Map (Compressed)
$E660 Spring Yard Green Map (Compressed)
$20000 Sonic Player Select Sprites
$212DF Tails Player Select Sprites
$22BE0 Eggman Player Select Sprites
$23220 Amy Player Select Sprites
$258C0 Green Hill Yellow Map (Compressed)
$25F56 Marble Yellow Map (Compressed)
$2661F Spring Yard Yellow Map (Compressed)
$26D6B Labyrinth Yellow Map (Compressed)
$27484 Star Light Yellow Map (Compressed)
$2C000 Labyrinth Green Map (Compressed)
$2C797 Green Hill Background (Compressed)
$2CFD9 Marble Background (Compressed)
$2D262 Spring Yard Background (Compressed)
$2D6A1 Labyrinth Background (Compressed)
$2DBFA Star Light Background (Compressed)
$2E244 Scrap Brain Background (Compressed)
$34000 Tails Uncompressed Sprites
$34C40 Amy Uncompressed Sprites
$35880 Eggman Uncompressed Sprites
$36500 Sonic Thumbs Up Sprite
$36660 Eggman Fist Pump Sprite
$367E0 Tails Peace Sign Sprite
$36940 Amy Waving Sprite
$38AC0 VS. Text Sprites (Compressed)
$38BEF Title Card Text Sprites (Compressed)
$3BC4F Sega Logo (Compressed)
$4339B Labyrinth Title Card Text (Compressed)
$45A5C Cursor on Menu Screen Sprite (Compressed)


Offset Description
$2131 Green Hill
$2151 Sonic/Blue Traffic Light
$2171 Marble
$2191 Spring Yard
$21B1 Labyrinth
$21D1 Star Light
$21F1 Scrap Brain
$3888 Track Rotating Palette
$45ABF Green Hill Course Select
$45AFF Marble Course Select


The text used on various screens can be edited via a hex editor. Each letter consists of two hex values, one representing the top of the letter, one representing the bottom. See Green Hill's text bellow for an example, the top of the letter is represented with a 1, while the bottom is represented with a 2 in the example:

           GT      RT      ET      ET      NT              HT
.db $00 $00 $46 $00 $4B $00 $2E $00 $2E $00 $47 $00 $00 $00 $41 $00
    IT       LT     LT              GB      RB     EB       EB
.db $42 $00 $45 $00 $45 $00 $00 $00 $50 $00 $5B $00 $3E $00 $3E $00
     NB             HB      IB      LB      LB
.db $57 $00 $00 $00 $51 $00 $52 $00 $55 $00 $55 $00

The text on the title cards follow a slightly different pattern, and the value for the letter "G" different. Each title card text consits of 96 bytes. The first two bytes determine the mappings' x and y positions on the screen. The last two bytes determine the letter mappings, the first byte is the top of the letter while the second byte is the bottom. Labyrinth uses both a compressed sprite and hex array for it's name. However, you can still easily edit the name as it follows the same format as the other track names. Here's Green Hill's Title Card Text:

"ROUND" Mappings, this is always the first line of text that displays and therefore appears before the actual track's name.

     X   Y   RT  X   Y   RB  X   Y   OT  X   Y   OB  X   Y   UT  X 
.db $3E $F0 $4B $46 $F0 $5B $3E $F8 $48 $46 $F8 $58 $3E $00 $4E $46
     Y   UB  X   Y   NT  X   Y   NB  X   Y   DT  X   Y   DB
.db $00 $5E $3E $08 $47 $46 $08 $57 $3E $10 $2D $46 $10 $3D 

Round Number Mappings (in this case it's 1)
     X   Y   1T   X   Y  1B
.db $3E $20 $82 $46 $20 $92

Unlike the mappings used on the results screen, the top and bottom of each letter appear in two bytes, each next to each other. See bellow:

     X   Y       X   Y   
.db $5E $00 $40 $66 $00 $50 G
.db $5E $08 $4B $66 $08 $5B R
.db $5E $10 $2E $66 $10 $3E E
.db $5E $18 $2E $66 $18 $3E E 
.db $5E $20 $47 $66 $20 $57 N
.db $6E $10 $41 $76 $10 $51 H 
.db $6E $18 $42 $76 $18 $52 I 
.db $6E $20 $45 $76 $20 $55 L
.db $6E $28 $45 $76 $28 $55 L 
.db $6E $30 $00 $76 $30 $00

Text Offsets

Offset Description
$15FEF SONIC Text on GP Results Screen
$160B3 TAILS Text on GP Results Screen
$16177 AMY Text on GP Results Screen
$1623B EGGMAN Text on GP Results Screen
$43445 Green Hill Title Card
$434A5 Marble Title Card
$43505 Spring Yard Title Card
$43565 Labyrinth Title Card
$435C5 Star Light Title Card
$43625 Scrap Brain Title Card
$4BCA1 Green Hill Grand Prix Results
$4BCCD Marble Grand Prix Results
$4BCF9 Spring Yard Grand Prix Results
$4BD25 Labyrinth Grand Prix Results
$4BD51 Star Light Grand Prix Results
$4BD7D Scrap Brain Grand Prix Results
$4AF3C Green Hill Free Run Results
$4AF68 Marble Free Run Results
$4AF94 Spring Yard Free Run Results
$4AFC0 Labyrinth Free Run Results
$4AFEC Star Light Free Run Results
$4B018 Scrap Brain Free Run Results
$4B170 Green Results Text
$4B18C Yellow Results Text
$4B1A8 Red Results Text

Letter Values

Offset Description
$00 Space/End of Line
$2A Top of A
$3A Bottom of A
$2B Top of B
$3B Bottom of B
$2C Top of C
$3C Bottom of C
$2D Top of D
$3D Bottom of D
$2E Top of E
$3E Bottom of E
$2F Top of F
$3F Bottom of F
$40 Top of G (Title Card Text)
$46 Top of G (Results Text)
$50 Bottom of G
$41 Top of H
$51 Bottom of H
$42 Top of I
$52 Bottom of I
$43 Top of J
$53 Bottom of J
$44 Top of K
$54 Bottom of K
$45 Top of L
$55 Bottom of L
$46 Top of M
$56 Bottom of M
$47 Top of N
$57 Bottom of N
$48 Top of O
$58 Bottom of O
$49 Top of P
$59 Bottom of P
$4A Top of Q
$5A Bottom of Q
$4B Top of R
$5B Bottom of R
$4C Top of S
$5C Bottom of S
$4D Top of T
$5D Bottom of T
$4E Top of U
$5E Bottom of U
$4F Top of V
$5F Bottom of V
$60 Top of W
$70 Bottom of W
$61 Top of X
$71 Bottom of X
$62 Top of Y
$72 Bottom of Y
$63 Top of Z
$73 Bottom of Z

Track Layouts

The track layout pointers are located at offset $361C. The first track is Green Hill Green which is located at offset $1D6A0, followed by Marble Green and so forth. Note that you'll need to edit each track map as well as the object layout for them to match your updated tracks. Each part of the track consists of three bytes. The first byte controls the background movement, while the second and third bytes are the actual track layout. Further research is needed in order to make edits to the track layouts.

Offset Description
$1D6A0 Green Hill Green
$1D6D0 Marble Green
$1D71A Spring Yard Green
$1D76E Labyrinth Green
$1D7C4 Star Light Green
$1D80E Scrap Brain Green
$1D859 Green Hill Red
$1D8AA Marble Red
$1D908 Spring Yard Red
$1D944 Labyrinth Red
$1D99A Star Light Red
$1D9DC Scrap Brain Red
$1DA47 Green Hill Yellow
$1DA8B Marble Yellow
$1DACF Spring Yard Yellow
$1DB0E Labyrinth Yellow
$1DB72 Star Light Yellow
$1DBC9 Scrap Brain Yellow


Music Pointers are located at offset $7D473 in the ROM. The sound effect pointers are located at $7D491.

Music Locations

Offset Description
$7D4D1 Options
$7D625 Title Screen
$7D6EE Green Hill
$7D940 Course Select With Intro
$7DB6E Spring Yard
$7DD79 Labyrinth
$7DF7D Star Light
$7E15A Scrap Brain
$7E494 Race Results
$7E511 GP Final Results
$7E5CC Invincibility Theme
$7E6B4 Credits
$7E838 Marble
$7E9F7 Course Select With No Intro


Sonic Drift
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