From c811dbd3445987bc219effbebc5499ba661b987b Mon Sep 17 00:00:00 2001
From: Vince Weaver <vince@deater.net>
Date: Fri, 23 Feb 2018 22:13:56 -0500
Subject: [PATCH] chiptune: shave 8 cycles off of dual 6522 write

---
 asm_routines/mockingboard_a.s     | 44 +++++++++++--------------------
 chiptune_player/chiptune_player.s |  2 +-
 2 files changed, 16 insertions(+), 30 deletions(-)

diff --git a/asm_routines/mockingboard_a.s b/asm_routines/mockingboard_a.s
index 54d06e19..fff7ca78 100644
--- a/asm_routines/mockingboard_a.s
+++ b/asm_routines/mockingboard_a.s
@@ -76,51 +76,37 @@ reset_ay_both:
 ;	Write sequence
 ;	Inactive -> Latch Address -> Inactive -> Write Data -> Inactive
 
-	;=======================
-	; Write Right AY-3-8910
-	;=======================
+	;=========================================
+	; Write Right/Left to save value AY-3-8910
+	;=========================================
 	; register in X
 	; value in MB_VALUE
 
 write_ay_both:
 	; address
-	stx	MOCK_6522_ORA1		; put address on PA		; 3
-	lda	#MOCK_AY_LATCH_ADDR	; latch_address on PB		; 2
-	sta	MOCK_6522_ORB1						; 3
+	stx	MOCK_6522_ORA1		; put address on PA1		; 3
+	stx	MOCK_6522_ORA2		; put address on PA2		; 3
+	lda	#MOCK_AY_LATCH_ADDR	; latch_address on PB1		; 2
+	sta	MOCK_6522_ORB1		; latch_address on PB1		; 3
+	sta	MOCK_6522_ORB2		; latch_address on PB2		; 3
 	lda	#MOCK_AY_INACTIVE	; go inactive			; 2
 	sta	MOCK_6522_ORB1						; 3
-
-	; value
-	lda	MB_VALUE						; 3
-	sta	MOCK_6522_ORA1		; put value on PA		; 3
-	lda	#MOCK_AY_WRITE		; write on PB			; 2
-	sta	MOCK_6522_ORB1						; 3
-	lda	#MOCK_AY_INACTIVE	; go inactive			; 2
-	sta	MOCK_6522_ORB1						; 3
-
-	;=======================
-	; Write Left AY-3-8910
-	;=======================
-
-;write_ay_left:
-	; address
-	stx	MOCK_6522_ORA2		; put address on PA		; 3
-	lda	#MOCK_AY_LATCH_ADDR	; latch_address on PB		; 2
-	sta	MOCK_6522_ORB2						; 3
-	lda	#MOCK_AY_INACTIVE	; go inactive			; 2
 	sta	MOCK_6522_ORB2						; 3
 
 	; value
 	lda	MB_VALUE						; 3
-	sta	MOCK_6522_ORA2		; put value on PA		; 3
-	lda	#MOCK_AY_WRITE		; write on PB			; 2
-	sta	MOCK_6522_ORB2						; 3
+	sta	MOCK_6522_ORA1		; put value on PA1		; 3
+	sta	MOCK_6522_ORA2		; put value on PA2		; 3
+	lda	#MOCK_AY_WRITE		;				; 2
+	sta	MOCK_6522_ORB1		; write on PB1			; 3
+	sta	MOCK_6522_ORB2		; write on PB2			; 3
 	lda	#MOCK_AY_INACTIVE	; go inactive			; 2
+	sta	MOCK_6522_ORB1						; 3
 	sta	MOCK_6522_ORB2						; 3
 
 	rts								; 6
 								;===========
-								;       61
+								;       53
 	;=======================================
 	; clear ay -- clear all 14 AY registers
 	; should silence the card
diff --git a/chiptune_player/chiptune_player.s b/chiptune_player/chiptune_player.s
index b93ab0c6..4a6b88e8 100644
--- a/chiptune_player/chiptune_player.s
+++ b/chiptune_player/chiptune_player.s
@@ -306,7 +306,7 @@ mb_not_13:
 	jsr	write_ay_both		; assume 3 channel (not six)	; 6
 					; so write same to both
 					; left/right
-									; 61
+									; 53
 
 	clc				; point to next interleaved	; 2
 	lda	INH			; page by adding $300		; 3