Optimize Text to HGR address by Mike B to save 1 byte

2017-07-24 11:42:17 -07:00 · 2017-07-24 11:42:17 -07:00 · 5122a0aaf9
parent 629866d97f
commit 5122a0aaf9
3 changed files with 3 additions and 4 deletions
--- a/BIN
+++ b/BIN
--- a/linuxlogo.s
+++ b/linuxlogo.s
@ -309,10 +309,9 @@ MakeShiftMask
        lda zTxtPtr+0   ; every 8 HGR scanline address
        sta zHgrPtr+0   ; is exactly same as Text low byte

-        lda zTxtPtr+1   
-        clc             ; every 8 HGR scanline address
-        adc #$1c        ; is Text Page $04 + $1C = HGR Page $20
-        sta zHgrPtr+1
+        lda zTxtPtr+1   ; every 8 HGR scanline address
+        eor #$24        ; is Text Page $04 + $1C = HGR Page $20; CLC, ADC #$1C
+        sta zHgrPtr+1   ; but we can optimize for HGR page 1 via EOR #$24 -- Thanks Mike B.!

 ; ------------------------------------------------------------------------
 ; Copy unpacked buffer to 8 HGR scanlines
--- a/ll_6502.dsk
+++ b/ll_6502.dsk