Streamlined Sonic Init

Streamlined init code for Sonic the Hedgehog 1, 2, and 3 & Knuckles made by OrionNavattan (under BSD Zero Clause).

The code targets SonicRetro's disassemblies, S1 Hivebrain 2022, and Sonic 2 OrnNv.

These are intended as drop-in replacements for the standard ICDBLK_4 library, and the game-specific init code that immediately follows. Compared to the original, these are streamlined, eliminating all redundancy (particularly on cold boot) and in-lining the VDP and joypad init, Z80 code load, and the checksum check (which is easy to remove!)

Installation Instructions

Sonic 1

AS (release v26.05, should work in later releases with adjustments)

• Replace everything from EntryPoint to MainGameLoop with the contents of Streamlined Sonic 1 Init AS.asm.
• Find GM_Title and delete the bsr.w DACDriverLoad instruction.
• Delete CheckSumError, VDPSetupGame, JoypadInit, and DACDriverLoad, as all of their functionality is incorporated into the new init code. (DACDriverLoad was called SoundDriverLoad before commit ea75d0f)

HB 2022

• Replace the Mega Drive Setup.asm include and all code from GameProgram to MainGameLoop with the contents of Streamlined Sonic 1 Init HB 2022.asm.
• Delete the same instruction and subroutines.

Sonic 2

AS

• Replace everything from EntryPoint to MainGameLoop with the contents of Streamlined Sonic 2 Init AS.asm.
• Delete CheckSumError, VDPSetupGame, JoypadInit, SoundDriverLoad, and DecompressSoundDriver up to the SaxDec_Loop label, as all of their functionality is incorporated into the new init code. (If you fail to do this, you will get a duplicate label/multiply defined error for movewZ80CompSize!)

OrnNv

• Essentially the same as Sonic 2 AS, except the file you need is Streamlined Sonic 2 Init Orion.asm.

Sonic 3K AS

Sonic 3 Alone

• Replace everything from EntryPoint up to Test_CountryCode (if you want to keep it) with the contents of Streamlined Sonic 3K Init AS.asm, uncommenting the Sonic 3 specific portions and removing the Sonic and Knuckles specific portions
• Delete the entirety of Test_Checksum, and

		lea	($FF0000).l,a6
		moveq	#0,d7
		move.w	#$3F7F,d6

loc_716:
		move.l	d7,(a6)+
		dbf	d6,loc_716

1 line after Test_Checksum_Done, then remove move.b #0,(Game_mode).w before GameLoop

• Delete Init_VDP, SndDrvInit, Init_Controllers and remove their branches.

Sonic & Knuckles/3 Complete

• Replace everything from EntryPoint up to Test_LockOn with the contents of Streamlined Sonic 3K Init AS.asm
• Delete Test_Checksum, the branches to it, and remove the following from Test_LockOn

		tst.w	(VDP_control_port).l
		move.w	#$4EF9,(V_int_jump).w	; machine code for jmp
		move.l	#VInt,(V_int_addr).w
		move.w	#$4EF9,(H_int_jump).w
		move.l	#HInt,(H_int_addr).w

-
		move.w	(VDP_control_port).l,d1
		btst	#1,d1
		bne.s	-	; wait till a DMA is completed
		lea	(RAM_start&$FFFFFF).l,a6
		moveq	#0,d7
		move.w	#bytesToLcnt(CrossResetRAM-RAM_start),d6

-
		move.l	d7,(a6)+
		dbf	d6,-

• Delete Init_VDP, SndDrvInit, Init_Controllers and their branches in BlueSpheresStartup, SonicAndKnucklesStartup, and ChecksumError2.
• bra.s SonicAndKnucklesStartup will cause an error, change bra.s to a bra.w