toinet
Inscrit le: 15 Juin 2007
Messages: 326
Localisation: Paris, France
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 Post� le: Jeu 09 Ao� 2007, 15:38 Sujet du message: Mastery Arithmetic Games 3.0 (Mastery Development, 1990) |
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Edu(ca)ware software from Mastery Development, the program contains different math subjects.
PROTECTION TYPE
On a DOS 3.3 type diskette, the header and data markers have been changed:
- Tracks 0 to 2 are readable and copyable (D5 AA 96, DE AA, D5 AA AD, DE AA)
- Tracks 3 to the end are protected (D5 AA AD, DE AA, D5 AA 96, DE AA)
DISK COPY
- Launch Advanced Demuffin
- Copy tracks 0 to 2 with standard parameters
- Go to the monitor
- B8FD: 96 (was AD)
- B96A: AD (was 96)
- Return to Advanced Demuffin (ctrl-y)
- Copy tracks 3 to the end of the diskette
PROTECTION REMOVAL
We now have to find the code that exchange the markers, it is located on track 2, sector 4 at offset $73:
| Code: | LDY #$96 ; parameters from track < 3
LDX #$AD
LDA $D546 ; which track are we on?
CMP #$03
BCC *+4 ; JMP if we are on track < 3
LDY #$AD ; parameters from tracks >= 3
LDX #$96 |
Solution 1
We have to exchange the second LDY LDX values...
- AD will become 96
- 96 will become AD
Solution 2
...or exchange LDY and LDX opcodes
- A0 (LDY) will become A2 (LDX)
- A2 (LDX) will become A0 (LDY)
If you have just chosen the first solution:
- Edit track 0, sector 2
- At offset $7F: change AD to 96
- At offset $81: change 96 to AD
- Save the sector
If you have just chosen the second solution:
- Edit track 0, sector 2
- At offset $7E: change A0 to A2
- At offset $80: change A2 to A0
- Save the sector
But choose and apply only ONE solution 
Your backup copy is now available,
Antoine |
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