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xmas2018: scrolling twice as fast, but at what cost?

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This commit is contained in:
Vince Weaver 2018-12-20 14:31:16 -05:00
parent 3e53efc75d
commit 6e854bf968
1 changed files with 96 additions and 13 deletions
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109
xmas_2018/merry.s
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@ -183,6 +183,7 @@ CURRENT = $01
NEXT = $02
COUNTH = $03
COUNTL = $04
OFFSCREEN = $05
;===========================================
;===========================================
@ -201,8 +202,9 @@ COUNTL = $04
; 10 check and loop
; 5 return
; total time = 13 + 140*(13+29+10+64*(41+30+2*(3727)))
; original time = 67,431,293 cycles = roughly 67s
; total time = 13 + 140*(13+29+10+64*(41+30+2*(3567)))
; 67,431,293 cycles = roughly 67s -- original
; 64,564,093 cycles = roughly 64s -- optimize inner loop a bit
scroll_hgr_left:
@ -233,17 +235,17 @@ left_one_loop:
; scroll second page
lda OUTH ; 3
sta TEMP ; 3
lda INH ; 3
sta OUTH ; 3
; lda OUTH ; 3
; sta TEMP ; 3
; lda INH ; 3
; sta OUTH ; 3
jsr hgr_scroll_line ; 6+???
; jsr hgr_scroll_line ; 6+???
; restore pointers
lda TEMP ; 3
sta OUTH ; 3
; lda TEMP ; 3
; sta OUTH ; 3
;============
; 30+2*???
@ -317,10 +319,94 @@ scroll_done:
hgr_scroll_line:
lda COUNTH
asl
clc
adc OUTL
sta INL
clc ; necessary?
lda OUTH
adc #$20
sta INH
ldy #0 ; 2
lda (INL),Y ; *
sta HIGH
ldx COUNTL
count0:
beq done_count ; if 0, need to do nothing
cpx #1
count1:
beq shiftright2 ; if 1, C>>2
cpx #2
count2:
beq shiftright4 ; if 2, C>>4
count3:
sta TEMP ; save C
iny
lda (INL),Y ; *
sta HIGH
cpx #3
bne not3
asl ; if 3, D<<1 | C>>6
and #$2
sta TEMPY
lda TEMP
lsr
lsr
lsr
lsr
lsr
lsr
and #$1
ora TEMPY
jmp done_count
not3:
cpx #4
count4:
beq shiftright1 ; if 4, D>>1
count5:
cpx #5
beq shiftright3 ; if 5, D>>3
count6: ; if 6, D>>5
shiftright5:
lsr
shiftright4:
lsr
shiftright3:
lsr
shiftright2:
lsr
shiftright1:
lsr
shiftright0:
done_count:
and #$7f
sta OFFSCREEN ; *
lda HIGH
and #$80
ora OFFSCREEN
sta OFFSCREEN
ldy #0 ; 2
ldy #0 ; 2
;===========
; 2
; repeated 40 times
hgr_scroll_line_loop:
lda (OUTL),Y ; get pixel block of interest ; 5
sta CURRENT ; 3
@ -329,10 +415,7 @@ hgr_scroll_line_loop:
bne not_thirtynine ; 3
thirtynine:
; -1
sty TEMPY ; save Y ; 3
ldy #0 ; 2
lda (INL),Y ; 5
ldy TEMPY ; restore Y ; 3
lda OFFSCREEN ; *
jmp done_thirtynine ; 3
not_thirtynine:
iny ; 2