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+====== Stable IRQ with DMA ======
+ChristopherJam's stable IRQ routine using DMA, posted on http://noname.c64.org/csdb/forums/?roomid=11&topicid=88971 (cleaned up and converted to ca65 syntax).
+<code asm>
+	.segment "STARTUP"
+	.word basicstub		; load address
+basicstub:
+	.word @nextline
+	.word 1970 + (.time / 31557600)
+	.byte $9e
+	.byte <(((init / 1000) .mod 10) + $30)
+	.byte <(((init / 100 ) .mod 10) + $30)
+	.byte <(((init / 10  ) .mod 10) + $30)
+	.byte <(((init       ) .mod 10) + $30)
+	.byte 0
+@nextline:
+	.word 0
+init:
+	lda #$04
+	sta $d021
+	sta 646
+	lda #147
+	jsr $ffd2
+	lda #0
+	sta $d021
+	lda #1		; something to see
+	sta $0400
+	lda #2
+	sta $0428
+	lda #$7f	; kill CIA irq
+	sta $dc0d
+	sei
+	lda #$35	; disable ROM
+	sta $01
+	lda #$01	; enable VIC irq
+	sta $d01a
+	lda #$1b	; clear high bit of irq rasterline
+	sta $d011
+	lda #$32	; last invisible line
+	sta $d012
+	lda #<irq1	; set irq vector
+	sta $fffe
+	lda #>irq1
+	sta $ffff
+	cli
+loop:
+	inc $07e7	; a nice untidy main loop to ensure instability!
+	bpl loop
+	jmp loop
+irq1:
+	pha
+	lda $d019
+	sta $d019
+	txa
+	pha
+	tya
+	pha
+	lda #$0f   ; this is unstable!
+	sta $d020
+	lda #$1a   ; force partial badline before screen starts
+	sta $d011
+	lda #$0b   ; this is stable ^_^
+	sta $d020
+	lda #$1b   ; trigger normal re-fetch of first row of chars
+	sta $d011
+	lda #$ff   ; set end-of-screen irq
+	sta $d012
+	lda #<irq2
+	sta $fffe
+	lda #>irq2
+	sta $ffff
+	pla
+	tay
+	pla
+	tax
+	pla
+	rti
+irq2:
+	pha
+	lda $d019
+	sta $d019
+	txa
+	pha
+	tya
+	pha
+	;ensure first row of chars is already being displayed when badline forced by irq1
+	lda #$18
+	sta $d011
+	lda #$32
+	sta $d012
+	lda #<irq1
+	sta $fffe
+	lda #>irq1
+	sta $ffff
+	pla
+	tay
+	pla
+	tax
+	pla
+	rti
+</code>