refactor(nsfdrv): Remove unnecessary init to 0

- fix: Fix multichip FDS padjumps

Author: Gumball2415

Source/drivers/FTDRV init variables.md

@@ -4,6 +4,9 @@ last updated: 2026-06-11
 
 ---
 
+Note that all these variables pertain to the initialization routine on driver
+versions 2.16 and below.
+
 ## variables init by `ft_music_init`
 
 - var_Linear_Counter `#$FF`
@@ -21,9 +24,9 @@ last updated: 2026-06-11
 - var_ch_TimerPeriodLo `#$00`
 - var_ch_TimerPeriodHi `#$00`
 - var_ch_Trigger `#$00`
-- var_ch_VibratoPos `#$00` (old vibrato mode)
-- var_ch_VibratoPos `#$48` (new vibrato mode)
-- var_ch_Note `#$80`
+- var_ch_VibratoPos `#$00` (new vibrato mode)
+- var_ch_VibratoPos `#$48` (old vibrato mode)
+- var_ch_Note `#$80` (DPCM)
 
 ### chip-specific init routines
 

Source/drivers/asm/build/build_engine.py

@@ -68,10 +68,11 @@ def build(chip: str):
     # headerless NSF kernel binary not supported
     if HEADERLESS:
         print("debug: NSF kernel binary not supported")
-        os.remove(f"out_{chip}{hdrless}.lst")
-        os.remove(f"c0_{chip}{hdrless}.bin")
-        os.remove(f"c1_{chip}{hdrless}.bin")
-        os.remove(f"driver_{chip}{hdrless}.o")
+        if not DEBUG:
+            os.remove(f"out_{chip}{hdrless}.lst")
+            os.remove(f"c0_{chip}{hdrless}.bin")
+            os.remove(f"c1_{chip}{hdrless}.bin")
+            os.remove(f"driver_{chip}{hdrless}.o")
         return
 
     adr = {}
@@ -90,7 +91,7 @@ def build(chip: str):
                 label = resolvelabel(label)
                 pos[label] = hexpos
                 adr[hexpos] = label
-            
+
             # search for label pointers to relocate
             relocsearch = re.search(r"(......).....(..)(.*[><])([\w]*).*;; Reloc$", line)
             if relocsearch is not None:

Source/drivers/asm/driver.s

@@ -501,36 +501,46 @@ PLAY:
 
 USE_PADJMP = 1  ; disable if you don't need FDS write protection
 
+;;
+; define a pad of nops, for areas that don't get executed
+; pads from startpad to endpad, inclusive
+.macro padnop startpad, endpad, condition
+	.local @padcount
+	@padcount = endpad-startpad+1
+	.if condition && USE_PADJMP
+.assert * = LOAD+((startpad-$8000) & $FFFF), warning, .sprintf("padding does not start at $%04X", startpad)
+		.repeat (@padcount)
+			nop
+		.endrep
+.assert * = LOAD+((endpad-$8000) & $FFFF)+1, warning, .sprintf("padding does not end after $%04X", endpad)
+	.endif
+.endmacro
+
 ;;
 ; manually define a jump command before padding as an optimization
+; pads from startpad to endpad, inclusive, and also including the jmp command
 .macro jmppad jump, startpad, endpad, condition
 	; count: bytes in total that the padding takes; must be more than 3
 	; count = (endpad - startpad)
-	.local @padcount
-	@padcount = endpad-startpad-2
-	.assert (endpad-startpad > 0), warning, .sprintf("padding byte size %d must be bigger than 3", @padcount)
 	.if condition && USE_PADJMP
-		.assert * = LOAD+((startpad-$8000) & $FFFF), warning, .sprintf("padding does not start at $%04X", startpad)
+.assert * = LOAD+((startpad-$8000) & $FFFF), warning, .sprintf("padding does not start at $%04X", startpad)
 			jump
-			.assert * = LOAD+((startpad+3-$8000) & $FFFF), warning, "jump command is not 3 bytes long"
-			.repeat (@padcount)
-				nop
-			.endrep
-		.assert * = LOAD+((endpad-$8000) & $FFFF)+1, warning, .sprintf("padding does not end after $%04X", endpad)
+.assert * = LOAD+((startpad+3-$8000) & $FFFF), warning, "jump command is not 3 bytes long"
+			padnop (startpad+3), endpad, condition
+.assert * = LOAD+((endpad-$8000) & $FFFF)+1, warning, .sprintf("padding does not end after $%04X", endpad)
 	.else
 		jump
 	.endif
 .endmacro
 
 ;;
 ; pads with NOPs and jmps to end of padding
-; @param startpad: start of register area to be padded with for assert, including the jmp command
-; @param endpad: end of register area to be padded with for assert
+; pads from startpad to endpad, inclusive, and also including the jmp command
 .macro padjmp startpad, endpad, condition
 	.if condition && USE_PADJMP
-		.local end
-		jmppad {jmp end}, startpad, endpad, condition
-		end:
+		.local @end
+		jmppad {jmp @end}, startpad, endpad, condition
+		@end:
 	.endif
 .endmacro
 

Source/drivers/asm/effects.s

@@ -160,17 +160,9 @@ ft_load_slide:
 @Done:
 	jsr ft_limit_note
 	sta var_ch_Note, x
-
-	; FDS scratch write padding: guard $9000-9003
-	padjmp $8FFC, $9003, .defined(USE_ALL) && .defined(PACKAGE)
-
 	sta var_ch_EchoBuffer, x		;;; ;; ;
 	jsr	ft_translate_freq_only
 	lda var_ch_TimerPeriodLo, x
-
-	; FDS scratch write padding: guard $9010
-	padjmp $900D, $9010, .defined(USE_ALL) && .defined(PACKAGE)
-
 	sta var_ch_PortaToLo, x
 	lda var_ch_TimerPeriodHi, x
 	sta var_ch_PortaToHi, x
@@ -187,10 +179,6 @@ ft_load_slide:
 	pla
 	sta var_ch_TimerPeriodLo, x
 	; change mode to sliding
-
-	; FDS scratch write padding: guard $9030
-	padjmp $902D, $9030, .defined(USE_ALL) && .defined(PACKAGE)
-
 	clc
 	lda var_ch_Effect, x
 	adc #01
@@ -203,10 +191,6 @@ ft_load_slide:
 	lda #EFF_SLIDE_DOWN
 	jmp :++
 :	lda #EFF_SLIDE_UP
-
-	; FDS scratch write padding: guard $9000-$9003
-	padjmp $8FFB, $9003, .defined(USE_ALL) && (.not .defined(PACKAGE))
-
 :
 .endif
 	sta var_ch_Effect, x
@@ -215,10 +199,6 @@ ft_load_slide:
 	lda ft_channel_type, x		;;; ;; ;
 .if .defined(USE_N163)
 	cpx #CHAN_N163
-
-	; FDS scratch write padding: guard $9010
-	padjmp $900C, $9010, .defined(USE_ALL) && (.not .defined(PACKAGE))
-
 	beq @Invert
 .endif
 	cpx #CHAN_NOI
@@ -229,20 +209,33 @@ ft_load_slide:
 	beq :+
 	lda #EFF_SLIDE_UP
 	sta var_ch_Effect, x
-:   lda #EFF_SLIDE_DOWN
+
+	; FDS scratch write padding: guard $9000-9003
+	padjmp $8FFB, $9003, .defined(USE_ALL) && .defined(PACKAGE)
+
+:	lda #EFF_SLIDE_DOWN
 	sta var_ch_Effect, x
 :
 
-	; FDS scratch write padding
-	jmppad {jmp ft_jump_to_effect}, $9028, $9030, .defined(USE_ALL) && (.not .defined(PACKAGE))
+
+	; FDS scratch write padding: guard $9000-$9003
+	jmppad {jmp ft_jump_to_effect}, $8FF8, $9003, .defined(USE_ALL) && !.defined(PACKAGE)
 
 ; see CChannelHandler::CalculatePeriod()
+
+	; FDS scratch write padding: guard $9010
+	padnop $900C, $9010, .defined(USE_ALL) && .defined(PACKAGE)
+
 ft_calc_period:
 
 	; Load period
 	lda var_ch_TimerPeriodLo, x
 	sta var_ch_PeriodCalcLo, x
 	lda var_ch_TimerPeriodHi, x
+
+	; FDS scratch write padding: guard $9010
+	padjmp $900D, $9010, .defined(USE_ALL) && !.defined(PACKAGE)
+
 	sta var_ch_PeriodCalcHi, x
 
 .if .defined(USE_VRC7)
@@ -254,9 +247,17 @@ ft_calc_period:
 	lda ft_channel_type, x
 	cmp #CHAN_VRC7
 	bne :+
+
+	; FDS scratch write padding: guard $9030
+	padjmp $902B, $9030, .defined(USE_ALL) && .defined(PACKAGE)
+
 	lsr var_ch_PeriodCalcHi, x
 	ror var_ch_PeriodCalcLo, x
 	lsr var_ch_PeriodCalcHi, x
+
+	; FDS scratch write padding: guard $9030
+	padjmp $902B, $9030, .defined(USE_ALL) && !.defined(PACKAGE)
+
 	ror var_ch_PeriodCalcLo, x
 :
 .endif

Source/drivers/asm/init.s

@@ -11,6 +11,7 @@ ft_music_init:
 	txa
 	pha ; region
 
+	; initialize all variables to #$00
 	lda #$00
 	; init variables in ZP
 	ldx #ZP_END
@@ -57,6 +58,7 @@ ft_music_init:
 	jsr ft_load_song
 
 	; Kill APU registers
+	lda #$00
 	ldx #$0B
 @LoadRegs:
 	sta $4000, x
@@ -88,52 +90,30 @@ ft_music_init:
 	sta var_ch_DPCM_EffPitch
 	sta var_ch_DPCMDAC
 
-	; Reset some variables for the wave channels
-	ldx #$00							;;; ;; ;
-:
-
-	cpx #(CH_COUNT_2A03 + CH_COUNT_MMC5)
-	bpl :+
+	; Reset channels with length counter
 	lda #$08
-	sta var_ch_LengthCounter, x			;;; ;; ;
-:	lda #$00
-	sta var_ch_NoteRelease, x			;;; ;; ;
-	sta var_ch_Transpose, x				;;; ;; ;
-	sta var_ch_NoteCut, x
-	sta var_ch_Effect, x
-	sta var_ch_EffParam, x
-	sta var_ch_PortaToLo, x
-	sta var_ch_PortaToHi, x
-	sta var_ch_TimerPeriodLo, x
-	sta var_ch_TimerPeriodHi, x
-	sta var_ch_Trigger, x				;;; ;; ;
-	inx
-	cpx #WAVE_CHANS
-	bne :--								; ;; ;;;
+	ldx #(CH_COUNT_2A03 + CH_COUNT_MMC5)
+:
+	dex
+	sta var_ch_LengthCounter, x
+	bne :-								; ;; ;;;
 
 .if .defined(USE_OLDVIBRATO)		;;; ;; ;
 	lda var_SongFlags
 	and #FLAG_OLDVIBRATO
-	beq :+
+	bne @SkipVibratoInit
 	lda #48
-:
-.endif
 	ldx #$00
 :	sta var_ch_VibratoPos, x
 	inx
 	cpx #WAVE_CHANS
 	bne :-
-.if .defined(USE_OLDVIBRATO)		;;; ;; ;
-	lda #$00
+@SkipVibratoInit:
 .endif
 
 	; DPCM
 .if .defined(USE_DPCM)
-	sta var_ch_NoteCut + DPCM_OFFSET
-	sta var_ch_NoteRelease + DPCM_OFFSET	;;; ;; ;
-.if .defined(USE_ALL)
-	ldx #EFF_CHANS
-.elseif .defined(USE_N163)
+.if .defined(USE_N163) && .not .defined(USE_ALL)
 	ldx var_EffChannels
 .else
 	ldx #EFF_CHANS
@@ -306,8 +286,8 @@ ft_load_song:
 	; Load the song
 	jsr ft_load_track
 
-	; Clear variables to zero
 	; Important!
+	; Variables should be initialized to 0 in ft_music_init
 	ldx #$01
 	stx var_PlayerFlags				; Player flags, bit 0 = playing
 	dex
@@ -318,20 +298,8 @@ ft_load_song:
 	lda #$80
 	sta var_ch_FinePitch, x
 	sta var_ch_VolSlideTarget, x	;; ;; !!
-	lda #$00
-
-	sta var_ch_VibratoSpeed, x
-	sta var_ch_TremoloSpeed, x
-	sta var_ch_Effect, x
-	sta var_ch_VolSlide, x
-	sta var_ch_NoteDelay, x
-	sta var_ch_ArpeggioCycle, x
-	sta var_ch_PhaseReset, x
-	sta var_ch_DPCMPhaseReset, x
-	sta var_ch_Harmonic, x
-	inc var_ch_Harmonic, x			; default value is 1
-	;
-	sta var_ch_Note, x
+	; all variables initialized to 0, but Kxx buffer should be 1
+	inc var_ch_Harmonic, x
 	inx
 
 	cpx #EFF_CHANS		;;; ;; ;
@@ -341,10 +309,6 @@ ft_load_song:
 	stx var_ch_PrevFreqHigh			; Set prev freq to FF for Sq1 & 2
 	stx var_ch_PrevFreqHigh + 1
 
-.if .defined(USE_DPCM)
-	lda #$00
-	sta var_ch_DPCM_Offset
-.endif
 .if .defined(USE_MMC5)
 	stx var_ch_PrevFreqHighMMC5
 	stx var_ch_PrevFreqHighMMC5 + 1
@@ -357,10 +321,6 @@ ft_load_song:
 	jsr ft_calculate_speed
 	;jsr ft_restore_speed
 
-	lda #$00
-	sta var_Tempo_Accum
-	sta var_Tempo_Accum + 1
-
 	rts
 
 ;

Source/drivers/asm/vrc7.s

@@ -374,10 +374,6 @@ ft_vrc7_get_freq:
 	lda #$00		;;; ;; ;
 	sta ACC 	; ;; ;;;
 	lda var_ch_vrc7_ActiveNote - VRC7_OFFSET, x
-
-	; FDS scratch write padding: guard $A000-$A002
-	padjmp $9FFC, $A002, .defined(USE_ALL) && .defined(PACKAGE)
-
 	jsr ft_translate_note_vrc7
 	tay
 
@@ -406,10 +402,6 @@ ft_vrc7_get_freq:
 @NoPorta:
 	lda ft_note_table_vrc7_l, y
 	sta var_ch_TimerPeriodLo, x
-
-	; FDS scratch write padding
-	padjmp $9FFD, $A002, .defined(USE_ALL) && (.not .defined(PACKAGE))
-
 	lda ft_note_table_vrc7_h, y
 	sta var_ch_TimerPeriodHi, x
 
@@ -429,9 +421,17 @@ ft_vrc7_get_freq_only:
 	sta ACC		; ;; ;;;
 	lda var_ch_vrc7_ActiveNote - VRC7_OFFSET, x
 	jsr ft_translate_note_vrc7
+
+	; FDS scratch write padding: guard $A000-$A002
+	padjmp $9FFD, $A002, .defined(USE_ALL) && .defined(PACKAGE)
+
 	tay
 	lda ft_note_table_vrc7_l, y
 	sta var_ch_TimerPeriodLo, x
+
+	; FDS scratch write padding: guard $A000-$A002
+	padjmp $9FFB, $A002, .defined(USE_ALL) && !.defined(PACKAGE)
+
 	lda ft_note_table_vrc7_h, y
 	sta var_ch_TimerPeriodHi, x