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toinet
Site Admin
Inscrit le: 15 Juin 2007
Messages: 3076
Localisation: Le Chesnay, France
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 Posté le: Sam 27 Fév 2021, 17:24 Sujet du message: Apple Writer II Pre-Boot Diskette (Videx, 1982) |
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#1042 - The is the pre-boot disk for Apple Writer II for owners of a Videx Videoterm 80 column video card.
Disk structure
It seems to be a DOS 3.3 disk. When we boot the disk, we have a DOS prompt.
An analysis with Locksmith Fast Disk Backup shows that no sector can be read.
Protection type
There is a long list of on-disk protection schemes here:
- a change of the sync mark (from FF to AB)
- a change of markers: D5AA96/FFFFFF and D5AAAD/FFFFFF
- a change of the nibble translation table (at $BA29)
- a nibble check (at $BB00)
How to copy
That is the easy part:
| Code: |
Boot my copy disk
Launch Advanced Demuffin 1.4
Insert the original disk in D1, a blank disk in D2
Press B to boot and grab the original RWTS
Copy the entire disk
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How to normalize
Boot my copy disk, launch Disk Fixer.
| Code: |
T0/S0/4B: FE BB --> FD 08 // skip the nibble check
T0/S2/3E: AB --> FF // restore the sync marker
T0/S2/4B: AB --> FF
T0/S2/9E: FF --> DE // restore the data field epilog markers
T0/S2/A3: FF --> AA
T0/S2/A8: FF --> EB
T0/S3/35: FF --> DE
T0/S3/3B: FF --> AA
T0/S3/91: FF --> DE // restore the addresss field epilog markers
T0/S3/9B: FF --> AA
T0/S4/29: AA --> 96 // restore the nibble translation table
T0/S4/7B: 60 --> EA // remove two RTS...
T0/S4/7C: 60 --> EA // ...to force the setting of the std marker values
T0/S6/30: FE --> FF // restore the sync marker
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You can see that the read addres field checks the epilog markers FFFF whereas the write address field writes DEAAEB. That is acceptable with that disk for a read/write session as the address field is not rewritten when a formatted sector is written. But it will not work after a format: init will write DEAAEB and read will search for FFFF. Bad bad bad.
The disk image is available at http://www.brutaldeluxe.fr/crack/
Reboot and... enjoy (fun may vary)
LoGo
2/2021 |
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toinet
Site Admin
Inscrit le: 15 Juin 2007
Messages: 3076
Localisation: Le Chesnay, France
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| Posté le: Sam 27 Fév 2021, 17:24 Sujet du message: |
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The nibble check at $BB00. It loops on a copy, it clears RAM and jumps to $B700 with an original disk.
| Code: |
0000:A9 FF LDA #$FF
0002:85 D6 STA $D6
0004:BD 8D C0 LDA $C08D,X
0007:BD 8E C0 LDA $C08E,X
000A:30 03 BMI $000F
000C:4C 0F BB JMP $BB0F
000F:AD FD FF LDA $FFFD
0012:C9 FA CMP #$FA
0014:D0 00 BNE $0016
0016:BD 8C C0 LDA $C08C,X
0019:A9 00 LDA #$00
001B:8D 00 02 STA $0200
001E:BD 8C C0 LDA $C08C,X
0021:10 FB BPL $001E
0023:C9 EB CMP #$EB
0025:D0 F7 BNE $001E
0027:BD 8C C0 LDA $C08C,X
002A:10 FB BPL $0027
002C:C9 D5 CMP #$D5
002E:D0 EE BNE $001E
0030:BD 8C C0 LDA $C08C,X
0033:10 FB BPL $0030
0035:C9 AA CMP #$AA
0037:D0 E5 BNE $001E
0039:A9 4C LDA #$4C
003B:A0 00 LDY #$00
003D:99 00 95 STA $9500,Y
0040:88 DEY
0041:D0 FA BNE $003D
0043:CE 3F BB DEC $BB3F
0046:AD 3F BB LDA $BB3F
0049:C9 07 CMP #$07
004B:D0 EC BNE $0039
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Bad sector, beware!!
T21/S5 is on file AW EUROPE
| Code: |
ADVANCED DEMUFFIN 1.4 - COPYRIGHT 1989
WRITTEN BY THE STACK AND THE BRAIN TRUST
=======PRESS ANY KEY TO CONTINUE========
TRK:.............R...R...............R.
+.5:
0123456789ABCDEF0123456789ABCDEF0123
SC0:...................................
SC1:...................................
SC2:...................................
SC3:...................................
SC4:...................................
SC5:.................................R.
SC6:...................................
SC7:...................................
SC8:...................................
SC9:...................................
SCA:...................................
SCB:...................................
SCC:...................................
SCD:...................................
SCE:...................................
SCF:...................................
========================================
16 SC $00,$00 TO $22,$0F BY 1.0 TO DRV 2
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