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101 lines
3.5 KiB
Plaintext
Executable File
101 lines
3.5 KiB
Plaintext
Executable File
;-------------------------------
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; #RPS
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; boot1 jumps to $B3C1 to change RWTS,
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; epilogue checker jumps to $B6B3 to
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; check timing bits, late DOS routes
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; through nibble check at $B74B
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;
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; so named because the disk volume string is
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; C1984 RPS A#
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;
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; variant 0
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; - Math Skills: Elementary Level (Encyclopaedia Britannica)
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; - Math Skills: Junior High Level (Encyclopaedia Britannica)
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; variant 1
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; - Dig Dug (Thunder Mountain)
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; - Pac-Man (Thunder Mountain)
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; - Galaxian (Thunder Mountain)
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;
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; variant 2
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; - Problem Solving in Algebra (Encyclopaedia Britannica)
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;-------------------------------
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!zone {
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; gTrack = 0
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; Caller found DOS 3.3 RWTS
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lda #$01
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ldx #$48
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jsr compare2 ; if T00,S01,$48 ==
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!byte $C1,$B3
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bcs .exit ; primary pattern not found, bail
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lda #$03
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ldx #$3E
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ldy #$04
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jsr compare ; if T00,S03,$3E ==
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!byte $4C,$B3,$B6
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!byte $EA
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bcs .variant0 ; passport-test-suite/Math Skills Elementary Level.woz [C=1] here
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jsr modify ; then set T00,S03,$3E =
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!byte $C9,$AA
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!byte $F0,$5C
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lda #$01 ; presence of JMP $B6B3 also indicates code at
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ldx #$48 ; $B41F that copies the real DOS code back to $B6B3
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; so we modify $B747 to jump to that (it exits via $9D84)
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jsr modify2 ; and set T00,S01,$48 =
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!byte $1F,$B4
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bvc .variant1 ; always branches
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.variant0
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lda #$01 ; lack of JMP $B6B3 indicates an earlier variant
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ldx #$48 ; which has no useful code at $B3C1, so we
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; modify $B747 to jump directly to $9D84
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jsr modify2
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!byte $84,$9D
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; /!\ execution falls through here
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.variant1
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;A=#$01 here regardless of how we got here
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;Y=#$02 here regardless of how we got here
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ldx #$87
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jsr compare3 ; if T00,S01,$87 ==
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!byte $6C,$58,$9D
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bcs .variant2 ; passport-test-suite/Pac-Man (Thunder Mountain).woz [C=0] here
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ldx #$8E
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jsr modify1 ; then set T00,S01,$8E =
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!byte $F8 ; change branch to unconditionally jump to success path
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ldx #$92
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jsr modify1 ; and set T00,S01,$92 =
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!byte $F1 ; change branch to unconditionally jump to success path
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bvc .rwtsswap ; always branches
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.variant2
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inx
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jsr compare3 ; if T00,S01,$88 ==
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!byte $6C,$58,$9D
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bcs .exit ; passport/test-suite/Problem Solving in Algebra.woz [C=0] here
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; if we didn't find indirect jump in either location, bail
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ldx #$8E ; variant #2 is similar to variant #1 but branch offsets differ by 1 byte
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jsr modify1 ; then set T00,S01,$8E =
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!byte $F9 ; change branch to unconditionally jump to success path
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ldx #$92
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jsr modify1 ; and set T00,S01,$92 =
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!byte $F2 ; change branch to unconditionally jump to success path
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.rwtsswap
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lda #$0C
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ldx #$40
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ldy #$04
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jsr compare
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!byte $32,$A2 ; MON and NOMON commands at $A233 and $A247
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!byte $46,$A2 ; are used to toggle protected/normal RWTS
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bcs .exit
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jsr modify
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!byte $57,$FF ; point them both to $FF58 (does nothing)
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!byte $57,$FF
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.exit
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}
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