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Difference between revisions of "Port the Sonic 2 Clone Sound Driver to the HG version of Sonic 2"

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{{GuideBy|Caverns4}}
 
{{GuideBy|Caverns4}}
 
==Summary==
 
==Summary==
−
The Sonic 2 Clone Driver is simply a modified version of the Sonic 1 Sound driver, designed to work with Sonic 2. The advantages to using this over the Sound Driver in Sonic 2 normally are numerous; It will be easier to modify existing songs as you won't have to worry about compressing and decompressing the music, and youre music will be supported by more up to date [[Music editor programs]].
+
<b>Please note that this guide is currently in need of a few teaks, which I will be implementing once I get the chance. In the meantime, use this guide at your own risk.</b> ~ Caverns4
 +
 
 +
The Sonic 2 Clone Driver is simply a modified version of the Sonic 1 Sound driver, designed to work with Sonic 2. The advantages to using this over the Sound Driver in Sonic 2 normally are numerous; It will be easier to modify existing songs as you won't have to worry about compressing and decompressing the music, and your music will be supported by more up to date [[Music editor programs]].
  
 
There are a few bugs I have noticed. One is that the spindash sound will not raise pitch. The music is not a perfect adaptation of Sonic 2's music, particularly sometimes the PSG channels sound slightly different. This is most noticeable in Emerald Hill's music. Besides this, there are no problems.
 
There are a few bugs I have noticed. One is that the spindash sound will not raise pitch. The music is not a perfect adaptation of Sonic 2's music, particularly sometimes the PSG channels sound slightly different. This is most noticeable in Emerald Hill's music. Besides this, there are no problems.

Revision as of 21:22, 26 July 2013

(Original guide by Caverns4)

Summary

Please note that this guide is currently in need of a few teaks, which I will be implementing once I get the chance. In the meantime, use this guide at your own risk. ~ Caverns4

The Sonic 2 Clone Driver is simply a modified version of the Sonic 1 Sound driver, designed to work with Sonic 2. The advantages to using this over the Sound Driver in Sonic 2 normally are numerous; It will be easier to modify existing songs as you won't have to worry about compressing and decompressing the music, and your music will be supported by more up to date Music editor programs.

There are a few bugs I have noticed. One is that the spindash sound will not raise pitch. The music is not a perfect adaptation of Sonic 2's music, particularly sometimes the PSG channels sound slightly different. This is most noticeable in Emerald Hill's music. Besides this, there are no problems.

If the above bugs will not bother you too badly, then you'll like using the Sonic 2 Clone Driver after working with Sonic 2's own sound driver. The Clone Driver is much easier to port music to, and in fact, Sonic 1 music can even just be bincluded into the ROM. This is because it's based on the Sonic 1 sound driver, and uses similar (if not the same) formatting. With this out of the way, now it's time to edit the Sonic 2 HG Dissasembly!

Before begining, you will need the following file:

Download.svg Download Sonic 2 Clone Driver Files
File: Sonic 2 Clone Driver.7z (78 kB) (info)

Step 1 - getting started

Back up your dissasembly if you haven't already.

To start, go into your sound folder, where you'll have a DAC folder, a music folder, and a PCM folder.

DELETE THEM ALL!

and then extract "Sonic 2 Clone Driver_fixed.7z" into the main folder of your dissasembly.

And then open up s2.sounddriver.asm, we're going to delete a lot of data from it.

Find zMasterPlaylist and delete the following lines: <asm>; zbyte_11F5h: zMasterPlaylist:

Music IDs

offset := MusicPoint2 ptrsize := 2 idstart := 80h

note
+20h means uncompressed, here
+40h is an (ignored) flag, possibly to force PAL mode on/off

zMusIDPtr_2PResult: db id(MusPtr_2PResult)  ; 92 zMusIDPtr_EHZ: db id(MusPtr_EHZ)  ; 81 zMusIDPtr_MCZ_2P: db id(MusPtr_MCZ_2P)  ; 85 zMusIDPtr_OOZ: db id(MusPtr_OOZ)  ; 8F zMusIDPtr_MTZ: db id(MusPtr_MTZ)  ; 82 zMusIDPtr_HTZ: db id(MusPtr_HTZ)  ; 94 zMusIDPtr_ARZ: db id(MusPtr_ARZ)  ; 86 zMusIDPtr_CNZ_2P: db id(MusPtr_CNZ_2P)  ; 80 zMusIDPtr_CNZ: db id(MusPtr_CNZ)  ; 83 zMusIDPtr_DEZ: db id(MusPtr_DEZ)  ; 87 zMusIDPtr_MCZ: db id(MusPtr_MCZ)  ; 84 zMusIDPtr_EHZ_2P: db id(MusPtr_EHZ_2P)  ; 91 zMusIDPtr_SCZ: db id(MusPtr_SCZ)  ; 8E zMusIDPtr_CPZ: db id(MusPtr_CPZ)  ; 8C zMusIDPtr_WFZ: db id(MusPtr_WFZ)  ; 90 zMusIDPtr_HPZ: db id(MusPtr_HPZ)  ; 9B zMusIDPtr_Options: db id(MusPtr_Options)  ; 89 zMusIDPtr_SpecStage: db id(MusPtr_SpecStage)  ; 88 zMusIDPtr_Boss: db id(MusPtr_Boss)  ; 8D zMusIDPtr_EndBoss: db id(MusPtr_EndBoss)  ; 8B zMusIDPtr_Ending: db id(MusPtr_Ending)  ; 8A zMusIDPtr_SuperSonic: db id(MusPtr_SuperSonic)  ; 93 zMusIDPtr_Invincible: db id(MusPtr_Invincible)  ; 99 zMusIDPtr_ExtraLife: db id(MusPtr_ExtraLife)+20h; B5 zMusIDPtr_Title: db id(MusPtr_Title)  ; 96 zMusIDPtr_EndLevel: db id(MusPtr_EndLevel)  ; 97 zMusIDPtr_GameOver: db id(MusPtr_GameOver)+20h  ; B8 zMusIDPtr_Continue: db (MusPtr_Continue-MusicPoint1)/ptrsize  ; 0 zMusIDPtr_Emerald: db id(MusPtr_Emerald)+20h  ; BA zMusIDPtr_Credits: db id(MusPtr_Credits)+20h  ; BD zMusIDPtr_Countdown: db id(MusPtr_Drowning)+40h  ; DC zMusIDPtr__End:</asm>

Then go to zDACMasterPlaylist, and delete these: <asm> db id(zDACPtr_Sample1),17h  ; 81h 

   db    id(zDACPtr_Sample2),1        ; 82h
   db    id(zDACPtr_Sample3),6        ; 83h
   db    id(zDACPtr_Sample4),8        ; 84h
   db    id(zDACPtr_Sample5),1Bh        ; 85h
   db    id(zDACPtr_Sample6),0Ah        ; 86h
   db    id(zDACPtr_Sample7),1Bh        ; 87h
   db    id(zDACPtr_Sample5),12h        ; 88h
   db    id(zDACPtr_Sample5),15h        ; 89h
   db    id(zDACPtr_Sample5),1Ch        ; 8Ah
   db    id(zDACPtr_Sample5),1Dh        ; 8Bh
   db    id(zDACPtr_Sample6),2        ; 8Ch
   db    id(zDACPtr_Sample6),5        ; 8Dh
   db    id(zDACPtr_Sample6),8        ; 8Eh
   db    id(zDACPtr_Sample7),8        ; 8Fh
   db    id(zDACPtr_Sample7),0Bh        ; 90h
   db    id(zDACPtr_Sample7),12h        ; 91h</asm>

Step 2 - Deleting broken references

Now open up s2.asm, and search for the line "; end of 'ROM'" near the end of your dissasemby.

On the empty line before it, past this:

<asm> include "Sonic 2 Clone Driver.asm" 

 even</asm>

After this, search for "SoundIndex:", and delete everything for it, up to and including "SndPtr__End:" Now there are many unused sounds, Sound20 - Sound70 in the dissasembly that will be unused. If you wish, delete those too, as

they will only take space.

Once you've done that, locate "MusicPoint2:", and delete that, and everything below it it until the following line:

<asm> if * > soundBankStart + $8000</asm>

Leave this line and everything below it alone for the time being.

Now find the line <asm>; loc_F1E8C:</asm>

Below this line is where the Sega sound is included. If we delete it, we will get errors. If we leave I, we will get errors. So what do we

do? Change it! Replace this: <asm>; -------------------------------------------------------------------------------

Sega Intro Sound
8-bit unsigned raw audio at 16Khz
-------------------------------------------------------------------------------
loc_F1E8C

Snd_Sega: BINCLUDE "sound/PCM/SEGA.bin" Snd_Sega_End: 

   if Snd_Sega_End - Snd_Sega > $8000
       fatal "Sega sound must fit within $8000 bytes, but you have a $\{Snd_Sega_End-Snd_Sega} byte Sega sound."
   endif
   if Snd_Sega_End - Snd_Sega > Size_of_SEGA_sound
       fatal "Size_of_SEGA_sound = $\{Size_of_SEGA_sound}, but you have a $\{Snd_Sega_End-Snd_Sega} byte Sega sound."
   endif</asm>

With this:

<asm>; loc_F1E8C: Snd_Sega: rts Snd_Sega_End:</asm>

Now, we need to delete the old BINCLUDEd DAC samples. Got to loc_ED100, or SndDAC_Start. Staring at line "; loc_ED100:", delete everything down to (But not including) this chunk of code.

<asm>; --------------------------------------------------------------------

Nemesis compressed art (20 blocks)
Buzzer's fireball

ArtNem_Buzzer_Fireball: BINCLUDE "art/nemesis/Fireball 1 (Buzzer).bin"

--------------------------------------------------------------------</asm>

That is art used in the game, so obviously we don't want that to get deleted.

Right above if, you will also see this line:

<asm> cnop -Size_of_DAC_samples, $8000</asm>

You need to delete that too.

Finally, search for sub_EC000, or "SoundDriverLoad", which will look like this:

<asm>; ---------------------------------------------------------------------------

Subroutine to load the sound driver
---------------------------------------------------------------------------
sub_EC000

SoundDriverLoad: 

   move    sr,-(sp)
   movem.l    d0-a6,-(sp)
   move    #$2700,sr
   lea    (Z80_Bus_Request).l,a3
   lea    (Z80_Reset).l,a2
   moveq    #0,d2
   move.w    #$100,d1
   move.w    d1,(a3)    ; get Z80 bus
   move.w    d1,(a2)    ; release Z80 reset (was held high by console on startup)

- btst d2,(a3) 

   bne.s    -    ; wait until the 68000 has the bus
   jsr    DecompressSoundDriver(pc)
   btst    #0,(VDP_control_port+1).l    ; check video mode
   sne    (Z80_RAM+zPalModeByte).l    ; set if PAL
   move.w    d2,(a2)    ; hold Z80 reset
   move.w    d2,(a3)    ; release Z80 bus
   moveq    #$E6,d0

- dbf d0,-  ; wait for 2,314 cycles 

   move.w    d1,(a2)    ; release Z80 reset
   movem.l    (sp)+,d0-a6
   move    (sp)+,sr
   rts</asm>
 
   Delete the whole thing, as it will now do nothing but cause an error.

Step 3 - Replace a bunch of stuff.

Search for the routine VintRet (Search for "VintRet:"), and you'll have something like this:

<asm>VintRet: 

   addq.l    #1,(Vint_runcount).w
   movem.l    (sp)+,d0-a6
   rte</asm>

Replace it with this:

<asm>VintRet: 

   jsr    Init_Sonic1_Sound_Driver    ; init Sonic 1 sound driver
   addq.l    #1,(Vint_runcount).w
   movem.l    (sp)+,d0-a6
   rte</asm>

Next, go to JmpTo_SoundDriverLoad, and find all of this:

<asm>JmpTo_SoundDriverLoad 

   nop

   jmp    (SoundDriverLoad).l
End of function JmpTo_SoundDriverLoad
===========================================================================
unused mostly-leftover subroutine to load the sound driver
SoundDriverLoadS1
   move.w    #$100,(Z80_Bus_Request).l ; stop the Z80
   move.w    #$100,(Z80_Reset).l; reset the Z80
   lea    (Z80_RAM).l,a1
   move.b    #$F3,(a1)+
   move.b    #$F3,(a1)+
   move.b    #$C3,(a1)+
   move.b    #0,(a1)+
   move.b    #0,(a1)+
   move.w    #0,(Z80_Reset).l
   nop
   nop
   nop
   nop
   move.w    #$100,(Z80_Reset).l ; reset the Z80
   move.w    #0,(Z80_Bus_Request).l ; start the Z80
   rts</asm>

and replace it like this:

<asm>JmpTo_SoundDriverLoad 

   move.w    #$100,(Z80_Bus_Request).l ; stop the Z80
   move.w    #$100,(Z80_Reset).l ; reset the Z80
   lea    (Kos_Z80).l,a0
   lea    (Z80_RAM).l,a1
   bsr.w    KosDec
   move.b    #$F3,(a1)+
   move.b    #$F3,(a1)+
   move.b    #$C3,(a1)+
   move.b    #0,(a1)+
   move.b    #0,(a1)+
   move.w    #0,(Z80_Reset).l
   nop
   nop
   nop
   nop
   move.w    #$100,(Z80_Reset).l ; reset the Z80
   move.w    #0,(Z80_Bus_Request).l ; start the Z80
   rts</asm>

Next, find PlayMusic, which should look like this this:

<asm>; sub_135E: PlayMusic: 

   tst.b    (Music_to_play).w
   bne.s    +
   move.b    d0,(Music_to_play).w
   rts

+ 

   move.b    d0,(Music_to_play_2).w
   rts
End of function PlayMusic</asm>

And replace it with this: <asm>; sub_135E: PlayMusic:

tst.b ($FFFFFFE0).w
bne.s +
move.b d0,($FFFFFFE0).w
   move.b    d0,($FFFFF00A).w
   rts

+ 

   move.b    d0,($FFFFF00A).w
   rts
End of function PlayMusic</asm>

Right beneath that should be PlaySound. Replace PlaySound with this: <asm>; sub_1370 PlaySound: 

   move.b    d0,($FFFFF00B).w
   rts
End of function PlaySound</asm>

Now we need to change PlaySoundStereo, which should be right beath PlaySound. Replace it with this: <asm>; sub_1376: PlaySoundStereo: 

   bra.s    PlayMusic    ; skip over routine (For S1 driver)
   move.b    d0,(SFX_to_play_2).w
   rts
End of function PlaySoundStereo</asm>

Now PlaySoundLocal is the next thing to edit, and again, it should be right below PlaySoundStereo. Replace it with this: <asm>; sub_137C: PlaySoundLocal: 

   tst.b    render_flags(a0)
   bpl.s    +
   move.b    d0,($FFFFF00B).w

+ 

   rts</asm>

Below this is the routine PauseGame. Rather than replacing that entire routine, we are simply going to find this:

<asm>+ 

   move.w    #1,(Game_paused).w    ; freeze time
   move.b    #MusID_Pause,(Music_to_play).w    ; pause music</asm>

And replace it with this:

<asm>+ 

   move.w    #1,(Game_paused).w    ; freeze time
   move.b    #1,($FFFFF003).w    ; pause music</asm>

Now go to Pause_Resume, which should look like this:

<asm>; loc_13F2: Pause_Resume: 

   move.b    #MusID_Unpause,(Music_to_play).w</asm>

Replace it with this:

<asm>; loc_13F2: Pause_Resume: 

   move.b    #$80,($FFFFF003).w</asm>

Now, find Pause_SlowMo, which should be this:

<asm>; loc_1400: Pause_SlowMo: 

   move.w    #1,(Game_paused).w
   move.b
   #MusID_Unpause,(Music_to_play).w
   rts</asm>

Replace it with the following:

<asm>; loc_1400: Pause_SlowMo: 

   move.w    #1,(Game_paused).w
   move.b    #1,($FFFFF003).w
   rts</asm>

Next, find SpecialStage_Unpause, which should be this:

<asm>; loc_541A: SpecialStage_Unpause: 

   move.b    #MusID_Unpause,(Music_to_play).w
   move.b    #8,(Vint_routine).w
   bra.w    WaitForVint</asm>

And replace it with this:

<asm>; loc_541A: SpecialStage_Unpause: 

   move.b    #1,($FFFFF003).w
   move.b    #8,(Vint_routine).w
   bra.w    WaitForVint</asm>

Finally, we're going to do something that will clean up some RAM for us later in the guide. Do a search and replace (Usually CTRL+H) for "Underwater_palette_2". Replace all with "Underwater_palette". I don't know why the game used two different section for underwater palettes, but I've done this change in my hack and it did no

harm.

We're done with the first part of this guide! Try to build your Rom, and you'll get some errors! Fun! Next up, we'll be fixing these errors.

Step 4 - Break it until it's fixed!

If you look at the log, you'll see a lot of errors like this one:

> > >Sonic 2 Clone Driver.asm(42): error: unknown opcode > > > INCBIN > > > PSG7: incbin sound\psg7.bin

Luckily, this is a simple fix. Open up Sonic 2 Clone Driver.asm, anf find and replace (CRTL+H usually) all instances of "INCBIN" with

"BINCLUDE" (Without the quotes, obviously).

Now repeat the process, replacing all intances of "@loc" with "Lloc". The HG dissasembly does not like local routines, so this

converts them into normal routines to avoid errors.

Save the file, and compile the ROM again. I got 437 errors, and of course, they need to be fixed as well.

On the bright side, you can close s2.asm and Sonic 2 Clone Driver.asn, they are all fixed.

Step 5 - Strippers

Re-Open s2.sounddriver.asm, because we need to strip it down even more.

Find zDACPtrTbl, and delete everything down to the line "idstart := 81h"

Go to "zBankSwitchToMusic:", and delete the contents of that routine.(Everything between "zBankSwitchToMusic:" and "ret" Go to "zUpdateDAC:" and again delete everything down to "ret".

Now find this line:

<asm>ensure1byteoffset macro maxsize</asm>

Delete everything between that and endm, but leave those two lines, otherwise you will get errors.

If you build the ROM now, you will get 393 errors, but almost all of these are duplicates or fixed just by fixing another. Don't close s2.sounddriver.asm just yet, we'll be stripping more content from that later. Right now however, we're going to fix the

bulk of these errors.

Step 6 - Identity Crisis

Open s2.constants.asm. 393 is a lot of errors, but all it takes to fix them is a copy+paste job for you.

Find the line "; Music IDs". You'll see this:

<asm>; Music IDs offset := zMasterPlaylist ptrsize := 1 idstart := $81

$80 is reserved for silence, so if you make idstart $80 or less,
you may need to insert a dummy zMusIDPtr in the $80 slot</asm>

delete everything from there down to "MusID__End = id(zMusIDPtr__End)  ; A0", and paste the following where it used to be:

<asm>; Music IDs offset := MusicIndex ptrsize := 1 idstart := $81

$80 is reserved for silence, so if you make idstart $80 or less,
you may need to insert a dummy zMusIDPtr in the $80 slot

MusID__First = idstart MusID_2PResult = $81 MusID_EHZ = $82 MusID_MCZ_2P = $83 MusID_OOZ = $84 MusID_MTZ = $85 MusID_HTZ = $86 MusID_ARZ = $87 MusID_CNZ_2P = $88 MusID_CNZ = $89 MusID_DEZ = $8A MusID_MCZ = $8B MusID_EHZ_2P = $8C MusID_SCZ = $8D MusID_CPZ = $8E MusID_WFZ = $8F MusID_HPZ = $90 MusID_Options = $91 MusID_SpecStage = $92 MusID_Boss = $93 MusID_EndBoss = $94 MusID_Ending = $95 MusID_SuperSonic = $96 MusID_Invincible = $97 MusID_ExtraLife = $98 MusID_Title = $99 MusID_EndLevel = $9A MusID_GameOver = $9B MusID_Continue = $9C MusID_Emerald = $9D MusID_Credits = $9E MusID_Countdown = $9F MusID__End = $A0</asm>

The music is all fixed, now all that's left is the sound effects:

Find the line "; Sound IDs", and delete everything down to the line "; Special sound IDs". Leve the special IDs alone.

In place of the text you deleted, just paste this:

<asm>; Sound IDs offset := SoundIndex ptrsize := 2 idstart := $A0

SndID__First = idstart SndID_Jump = $A0  ; A0 SndID_Checkpoint = $A1  ; A1 SndID_SpikeSwitch = $A2  ; A2 SndID_Hurt = $A3  ; A3 SndID_Skidding = $A4  ; A4 SndID_BlockPush = $A5  ; A5 SndID_HurtBySpikes = $A6  ; A6 SndID_Sparkle = $A7 SndID_Beep = $A8 SndID_Bwoop = $A9 SndID_Splash = $AA SndID_Swish = $AB SndID_BossHit = $AC SndID_InhalingBubble = $AD SndID_ArrowFiring = $AE SndID_LavaBall = $AE SndID_Shield = $Af SndID_LaserBeam = $B0 SndID_Zap = $B1 SndID_Drown = $B2 SndID_FireBurn = $B3 SndID_Bumper = $B4 SndID_Ring = $B5  ; B5 SndID_RingRight = $B5 SndID_SpikesMove = $B6 SndID_Rumbling = $B7 SndID_Smash = $B9 SndID_DoorSlam = $BB SndID_SpindashRelease = $BC  ; BC SndID_Hammer = $BD SndID_Roll = $BE SndID_ContinueJingle = $BF SndID_CasinoBonus = $C0 SndID_Explosion = $C1 SndID_WaterWarning = $C2 SndID_EnterGiantRing = $C3 SndID_BossExplosion = $C4 SndID_TallyEnd = $C5 SndID_RingSpill = $C6 SndID_Flamethrower = $C8 SndID_Bonus = $C9 SndID_SpecStageEntry = $CA SndID_SlowSmash = $CB SndID_Spring = $CC SndID_Blip = $CD SndID_RingLeft = $B5 SndID_Signpost = $CF SndID_CNZBossZap = $D0 SndID_Signpost2P = $D3 SndID_OOZLidPop = $D4 SndID_SlidingSpike = $D5 SndID_CNZElevator = $D6 SndID_PlatformKnock = $D7 SndID_BonusBumper = $D8 SndID_LargeBumper = $D9 SndID_Gloop = $DA SndID_PreArrowFiring = $DB SndID_Fire = $DC SndID_ArrowStick = $DD SndID_Helicopter = $DE SndID_SuperTransform = $DF SndID_SpindashRev = $E0 SndID_Rumbling2 = $E1 SndID_CNZLaunch = $E2 SndID_Flipper = $E3 SndID_HTZLiftClick = $E4 SndID_Leaves = $E5 SndID_MegaMackDrop = $E6 SndID_DrawbridgeMove = $E7 SndID_QuickDoorSlam = $E8 SndID_DrawbridgeDown = $E9 SndID_LaserBurst = $EA SndID_Scatter = $EB SndID_LaserFloor = $EB SndID_Teleport = $EC SndID_Error = $ED SndID_MechaSonicBuzz = $EE SndID_LargeLaser = $EF SndID_OilSlide = $F0 SndID__End = $F7</asm>

Step 7 - I am Error

Now we are going back to s2.sounddriver.asm. There are 4 more errors here. As before, we're going to solve this by simply emptying out the relavent routines. We can't just delete stuff because a few things in it

are still going to be referenced. So the first Routine to clean out is zDACAfterDur. change that and remove zloc_22A inside it so it looks like this:

<asm>zDACAfterDur: 

   ret</asm>

There is one more routine to empty. That routine is zloc_78E, or zBGMLoad. Starting at this line:

<asm>zBGMLoad:</asm>

delete everything down to here:

<asm>  ; End of DAC/FM init, begin PSG init</asm>

And there you have it! Close s2.sounddriver.asm, Build you ROM and test it!

Additional Step

Uh-oh! if you've played up to Chemical Plant Zone Act 2, you'll notice the driver crashes on that level!

This is because of water. In Sonic 2, the underwater palettes are stored in a section of RAM that is now used by the sound driver,

because it's based on Sonic 1's sound driver. What we need to do now is relocate the water palette table in RAM, so the Sound Driver can do what it likes. I am going to assume

you haven't modified the RAM allocation in your hack here, and go step by step. If you have modifying the RAM in your game, you

are probably on your own.

Let's go back to s2.constants.asm, and find these lines:

<asm>Underwater_palette_2: ds.w palette_line_size  ; not sure what it's used for but it's only used when there's water Underwater_palette_2_line2: ds.w palette_line_size Underwater_palette_2_line3: ds.w palette_line_size Underwater_palette_2_line4: ds.w palette_line_size

Underwater_palette: ds.w palette_line_size  ; main palette for underwater parts of the screen Underwater_palette_line2: ds.w palette_line_size Underwater_palette_line3: ds.w palette_line_size Underwater_palette_line4: ds.w palette_line_size 

               ds.b    $500    ; $FFFFF100-$FFFFF5FF ; unused, leftover from the Sonic 1 sound driver (and used by it when you port it to

Sonic 2) </asm> The last four lines before the ds.b $500 are used by the sound driver now, in addition to the 500 that is labeled as such.

Replace all of the above lines with this:

<asm> ds.b $100  ; Sonic 1 Sound Driver 

                   ds.b    $500    ; Sonic 1 Sound Driver</asm>

After doing that, you will need to find at least $80 free bytes in RAM (besides the space we just put in) Fortunately, there is an area of RAM that has $C0 free bytes, and that is where the four lines we lost will go. Search for this:

<asm>CNZ_saucer_data:</asm>

And you will see this:

<asm>CNZ_saucer_data: ds.b $40  ; the number of saucer bumpers in a group which have been destroyed. Used to decide when to give 500 points instead of 10 

               ds.b    $C0    ; $FFFFE740-$FFFFE7FF ; unused as far as I can tell

Ring_Positions: ds.b $600</asm>

Replace it with this:

<asm>CNZ_saucer_data: ds.b $40  ; the number of saucer bumpers in a group which have been destroyed. Used to decide when to give 500 points instead of 10 Underwater_palette: ds.w palette_line_size  ; main palette for underwater parts of the screen Underwater_palette_line2: ds.w palette_line_size Underwater_palette_line3: ds.w palette_line_size Underwater_palette_line4: ds.w palette_line_size 

               ds.b    $40    ; $FFFFE740-$FFFFE7FF ; unused as far as I can tell

Ring_Positions: ds.b $600</asm>

Build it, and test!

The sega sound will be glitched up, and you can fix it by following this link. Everything that needs to be fixed will be in "Sonic 2 Clone Driver.asm".

Credits

   Varion Icaria - Puto's sound driver port.
   Esrael - Tweakers driver port, plus fixes for things broken in Puto's port, such as hanging on the title card. Extra thanks for fixing the Sega sound.
   Puto - Fixes for underwater palette stuff, as well as special stage ring stuff, and various other fixes to the original guide.
   Tweaker - Wrote the orignal guide to port Sonic 1's sound driver into Sonic 2.
   ValleyBell - lots of miscallanious help to get this to work, as well as worked on the Sonic 2 Clone Driver.
   ShadowsofYesterday - Telling me the fix for the SEGA sound.
   Caverns4 - I wrote this guide!
SCHG How-To Guide: Sonic the Hedgehog 2 (16-bit)
Fixing Bugs
Fix Demo Playback | Fix a Race Condition with Pattern Load Cues | Fix Super Sonic Bugs | Use Correct Height When Roll Jumping | Fix Jump Height Bug When Exiting Water | Fix Screen Boundary Spin Dash Bug | Correct Drowning Bugs | Fix Camera Y Position for Tails | Fix Tails Subanimation Error | Fix Tails' Respawn Speeds | Fix Accidental Deletion of Scattered Rings | Fix Ring Timers | Fix Rexon Crash | Fix Monitor Collision Bug | Fix EHZ Deformation Bug | Correct CPZ Boss Attack Behavior | Fix Bug in ARZ Boss Arrow's Platform Behavior | Fix ARZ Boss Walking on Air Glitch | Fix ARZ Boss Sprite Behavior | Fix Multiple CNZ Boss Bugs | Fix HTZ Background Scrolling Mountains | Fix OOZ Launcher Speed Up Glitch | Fix DEZ Giant Mech Collision Glitch | Fix Boss Deconstruction Behavior | Fix Speed Bugs | Fix 14 Continues Cheat | Fix Debug Mode Crash | Fix 99+ Lives | Fix Sonic 2's Sega Screen
Design Choices
Remove the Air Speed Cap | Disable Floor Collision While Dying | Modify Super Sonic Transformation Methods & Behavior | Enable/Disable Tails in Certain Levels | Collide with Water After Being Hurt | Retain Rings When Returning at a Star Post | Improve the Fade In\Fade Out Progression Routines | Fix Scattered Rings' Underwater Physics | Insert LZ Water Ripple Effect | Restore Lost CPZ Boss Feature | Prevent SCZ Tornado Spin Dash Death | Improve ObjectMove Subroutines | Port S3K Rings Manager | Port S3K Object Manager | Port S3K Priority Manager | Edit Level Order with ASM‎ | Alter Ring Requirements in Special Stages | Make Special Stage Characters Use Normal DPLCs | Speed Up Ring Loss Process | Change spike behaviour in Sonic 2
Adding Features
Create Insta-kill and High Jump Monitors | Create Clone and Special Stage Monitors | Port Knuckles
Sound Features
Expand Music Index to Start at $00 | Port Sonic 1 Sound Driver | Port Sonic 2 Clone Driver | Port Sonic 3 Sound Driver | Port Flamewing's Sonic 3 & Knuckles Sound Driver | Expand the Music Index to Start at $00 (Sonic 2 Clone Driver Version) | Play Different Songs Per Act
Extending the Game
Extend the Level Index Past $10 | Extend the Level Select | Extend Water Tables | Add Extra Characters | Free Up 2 Universal SSTs
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