From 406a0628bd30aaa72a73d72205f82cb960312ae8 Mon Sep 17 00:00:00 2001
From: Oliver Schmidt <ol.sc@web.de>
Date: Tue, 12 May 2020 23:01:21 +0200
Subject: [PATCH] Removed unnecessary zero page usage.

LDY <absolute>,X without page-crossing (sort of surprisingly) requires only 4 cycles, so there's after all no need at all to resort to LDY <zeropage>,X to stay inside the 4 cycle budget.
---
 stream.s | 50 +++++++++++++-------------------------------------
 1 file changed, 13 insertions(+), 37 deletions(-)

diff --git a/stream.s b/stream.s
index e18a904..04ef819 100644
--- a/stream.s
+++ b/stream.s
@@ -5,17 +5,18 @@
 .macpack    apple2
 .pc02
 
-src         := $00
-dst         := $02
-rd_count    := $04
-wr_count    := $05
-scroll_row  := $06
-scroll_col  := $07
-scroll_opc  := $08
+; free zero page locations according to ProDOS TechRefMan A.4
+src         := $CE
+dst         := $D6
+rd_count    := $EB
+wr_count    := $EC
+scroll_row  := $ED
+scroll_col  := $EE
+scroll_opc  := $EF
 
 program     := $100B        ; adressed via jmp_table !
 buffer      := $9000
-zp_save     := $9100
+physical    := $9100
 
 px          = $8F           ; force page crossing
 silence     = $FF
@@ -118,22 +119,15 @@ chr:lda a:$0000,x           ; patched
 
 
 stream:
-    ; Save zero page
-    ldx #$00
-:   lda $00,x
-    sta zp_save,x
-    inx
-    bne :-
-
     ; Crate unrolled loop program
     jsr unroll
 
-    ; Create socket 0 physical read memory lookup table in zero page
+    ; Create socket 0 physical read memory lookup table
     ldx #$00
 :   txa
     and #>$1FFF
     ora #>$6000
-    sta $00,x
+    sta physical,x
     inx
     bne :-
 
@@ -152,13 +146,6 @@ stream:
     ; Run unrolled loop program
     jsr program
 
-    ; Restore zero page
-    ldx #$00
-:   lda zp_save,x
-    sta $00,x
-    inx
-    bne :-
-
     ; Switch to text screen
     bit $C051
 
@@ -473,17 +460,6 @@ scroll_patch:
 :.endmacro
 
 
-; 14 bytes, 9 cycles
-.macro      spkr_long
-    lsr a                   ;   2
-    bcs :+                  ;   2   3
-    nop                     ;   2
-    bra :++                 ;   3
-    .res 5
-:   bit $C030               ;       4
-:.endmacro
-
-
 ; 13 bytes, 9 cycles
 .macro      spkr_jsr    addr
     lsr a                   ;   2
@@ -550,8 +526,8 @@ recv_prolog:
     spkr                    ; bit 2
     ldx $C0F7               ; high byte
     spkr                    ; bit 3
-    ldy $00,x               ; high byte -> physical
-    spkr_long               ; bit 4
+    ldy physical,x          ; high byte -> physical
+    spkr                    ; bit 4
     ldx $C0F7               ; low byte
     spkr                    ; bit 5
     sty $C0F5               ; read addr high