1a0ce36a69
Findings of note: - The LCD (PPU) can seemingly end up at a cycle offset relative to the CPU that is a non-multiple of 4 when switching away from double speed mode (as compared with normal). The behaviour appears equivalent to a CPU tick being skipped relative to the LCD/PPU, which can result in 2 different offsets depending on whether the speed change is done at an odd M-cycle (i.e. an odd multiple of 4 cycles in double speed mode). This will also seemingly carry over to double speed mode upon another speed change, and, repeated speed changes can seemingly produce all 4 offsets.
127 lines
1.7 KiB
NASM
127 lines
1.7 KiB
NASM
.size 8000
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.text@50
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jp ltimaint
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.text@100
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jp lbegin
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.data@143
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c0
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.text@150
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lbegin:
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xor a, a
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ldff(06), a
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ld a, 05
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ldff(07), a
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ld a, f0
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ldff(05), a
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ld a, 04
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ldff(ff), a
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xor a, a
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ldff(0f), a
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ei
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.text@1000
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ltimaint:
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nop
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ld a, 30
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ldff(00), a
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xor a, a
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ldff(ff), a
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inc a
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ldff(4d), a
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stop, 00
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nop
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ldff a, (05)
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jp lprint_a
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.text@7000
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lprint_a:
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push af
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ld b, 91
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call lwaitly_b
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xor a, a
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ldff(40), a
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ld bc, 7a00
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ld hl, 8000
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ld d, 00
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lprint_copytiles:
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ld a, (bc)
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inc bc
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ld(hl++), a
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dec d
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jrnz lprint_copytiles
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pop af
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ld b, a
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swap a
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and a, 0f
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ld(9800), a
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ld a, b
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and a, 0f
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ld(9801), a
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ld a, c0
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ldff(47), a
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ld a, 80
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ldff(68), a
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ld a, ff
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ldff(69), a
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ldff(69), a
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ldff(69), a
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ldff(69), a
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ldff(69), a
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ldff(69), a
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xor a, a
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ldff(69), a
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ldff(69), a
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ldff(43), a
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ld a, 91
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ldff(40), a
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lprint_limbo:
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jr lprint_limbo
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.text@7400
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lwaitly_b:
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ld c, 44
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lwaitly_b_loop:
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ldff a, (c)
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cmp a, b
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jrnz lwaitly_b_loop
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ret
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.data@7a00
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00 00 7f 7f 41 41 41 41
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41 41 41 41 41 41 7f 7f
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00 00 08 08 08 08 08 08
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08 08 08 08 08 08 08 08
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00 00 7f 7f 01 01 01 01
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7f 7f 40 40 40 40 7f 7f
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00 00 7f 7f 01 01 01 01
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3f 3f 01 01 01 01 7f 7f
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00 00 41 41 41 41 41 41
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7f 7f 01 01 01 01 01 01
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00 00 7f 7f 40 40 40 40
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7e 7e 01 01 01 01 7e 7e
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00 00 7f 7f 40 40 40 40
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7f 7f 41 41 41 41 7f 7f
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00 00 7f 7f 01 01 02 02
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04 04 08 08 10 10 10 10
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00 00 3e 3e 41 41 41 41
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3e 3e 41 41 41 41 3e 3e
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00 00 7f 7f 41 41 41 41
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7f 7f 01 01 01 01 7f 7f
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00 00 08 08 22 22 41 41
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7f 7f 41 41 41 41 41 41
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00 00 7e 7e 41 41 41 41
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7e 7e 41 41 41 41 7e 7e
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00 00 3e 3e 41 41 40 40
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40 40 40 40 41 41 3e 3e
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00 00 7e 7e 41 41 41 41
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41 41 41 41 41 41 7e 7e
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00 00 7f 7f 40 40 40 40
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7f 7f 40 40 40 40 7f 7f
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00 00 7f 7f 40 40 40 40
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7f 7f 40 40 40 40 40 40
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