The Glitch Apple Disk Collection/2014.glitch.apple.collection.zip/indexed/CRACK83.DSK/FILE #11.txt

Text File | 2014-09-09 | 6KB | 119 lines

MSG LEFT BY: TRYSTAN II


THIS AND  THE FOLLOWING  MESSAGE ARE  BOTH  FORMATTED  FOR 80  COLUMNS.  BE
SURE TO USE THE VIDEO COMMAND TO CHANGE YOUR SCREEN WIDTH!

THRESHOLD IS THE FIRST GAME PROGRAM WHICH USES DISK ACCESS DURING PLAY THAT
I  HAVE  BEEN  ABLE  TO  CRACK.   I HOPE THE TECHNIQUE DESCRIBED BELOW WILL
ENABLE SOME OF THE OTHER DISK-BASED GAMES TO UNFOLD THEIR  MANIFEST  CHARMS
TO THE WORLD OF DOS 3.3!

FIRST, THE SIMPLE PART--THAT OF GETTING THE MAIN CODE INTO A NORMAL DOS 3.3
BINARY FILE:

           1)  BOOT THRESHOLD NORMALLY.  WHEN YOU GET TO THE POINT WHERE IT
ASKS YOU WHETHER YOU WANT TO USE PADDLES OR KEYBOARD, PRESS RESET.  THIS IS
WHERE THE GAME WILL START ONCE IT'S BROKEN.  THE LOGO IS NICE, BUT  USELESS
AND,  SINCE  THRESHOLD  USES RAM FROM $800 TO $B600, YOU DON'T HAVE ROOM TO
LOAD IT WITH NORMAL DOS.

           2)  YOU NOW HAVE TO SAVE EVERYTHING IN MEMORY FROM 0  TO  $98FF,
EXCEPT  FOR  HI-RES PAGE 1 ($2000-$3FFF).  SAVING PAGES 0-7 IS THE HARDEST,
SINCE RESET LIKES TO WALK ALL OVER VARIOUS PARTS OF IT.  BECAUSE  OF  THIS,
YOU  NEED  TO USE SOMETHING TO RELOCATE THE FIRST 8 PAGES OF MEMORY UP TO A
LOCATION LIKE $1000 OR SO, WHICH WILL ENABLE  YOU  TO  RE-BOOT  NORMAL  DOS
WITHOUT WIPING IT OUT.  I USED MASTER KEY+ TO SAVE ALL THE PARTS, INCLUDING
PAGE 0-7.  FROM WHAT I GATHER, ONE OF THE TWO CRACKING ROMS IN THE DOWNLOAD
SECTION WILL ALSO RELOCATE PAGES 0-7 UPON HITTING RESET.
             3)   ONCE YOU HAVE SAVE PAGES 0-7, YOU NEED TO RE-BOOT THRESHOLD
IN ORDER TO SAVE PAGES 8 THRU $97 ($800-$97FF).  THIS IS A BIT EASIER,  BUT
YOU  HAVE  TO  REMEMBER  TO  MOVE  PAGE 8 OUT OF THE WAY BEFORE YOU RE-BOOT
NORMAL DOS BECAUSE IT GETS CLOBBERED.  YOU SHOULD DO THIS IN TWO STAGES  IN
ORDER  TO  MAKE  THE  RELOCATION PROCESS (DESCRIBED BELOW) EASIER.  I FIRST
SAVED $800-$1FFF, THEN RE-BOOTED THRESHOLD, AND MOVED $4000-$97FF  DOWN  TO
$2000 BEFORE SAVING IT.

           4)  NOW ALL YOU DO IS BLOAD THE THREE PIECES LIKE SO:

               A)  BLOAD THE $800-$1FFF FILE AT $800
               B)  BLOAD THE PAGE 0-7 FILE AT $2000
               C)  BLOAD THE $4000-$97FF FILE AT $2800

THE  PROGRAM NOW RESIDES IN MEMORY FROM $800-$80FF.  THE ONLY THING LEFT IS
TO WRITE A LITTLE ASSEMBLY LANGUAGE ROUTINE TO RELOCATE PAGES 0-7 AND
$2800-$80FF  TO THEIR PROPER ADDRESSES.  HINT: USE THE MOVE ROUTINES IN THE
MONITOR!  I PUT MY CODE RELOCATOR AT $8100 AND ADDED A JUMP TO IT AT  $7FD.
FINALLY,  ADD  A  JUMP  TO THE STARTING ADDRESS OF $6B00 AT THE END OF YOUR
RELOCATION ROUTINE.  THEN, A BSAVE THRESHOLD,A$7FD,L$7A03 WILL SAVE IT  ALL
IN ONE EXECUTABLE CHUNK.  BY USING A LENGTH OF $7A03, YOU GIVE YOURSELF 255
BYTES IN WHICH TO WRITE YOUR RELOCATION CODE.

THE TECHNIQUE OF PULLING THE  PIECES  OF  THE  DISK  ACCESSED  DURING  PLAY
FOLLOWS IN THE NEXT MESSAGE.









THE MOST DIFFICULT PART OF CRACKING THRESHOLD IS SAVING  THE  VARIOUS  BITS
AND PIECES OF THE DISK THAT IT ACCESSES DURING PLAY.

THE  CODE STARTING AT $9383 SETS UP THE IOB AND CALLS THE RWTS TO LOAD IN 3
SEPARATE "FILES" EACH TIME YOU ADVANCE TO A NEW  LEVEL.   FORTUNATELY,  THE
RWTS IN THRESHOLD IS NOT TOO HEAVILY MODIFIED, SO YOU CAN USE THE INSPECTOR
TO READ THE THRESHOLD DISK.  BEFORE YOU START READING THE  THRESHOLD  DISK,
YOU  WILL  HAVE  TO CHANGE LOCATION $3D9 TO JUMP TO THE RWTS AT $B7B5 (I.E.
3D9:4C B5 B7) AND THEN CHANGE THE RESET VECTOR TO JUMP  TO  SOME  INNOCUOUS
LOCATION SO THAT YOU CAN RESET OUT OF THE INSPECTOR.

STARTING  AT  $9383,  YOU WILL FIND 3 CALLS TO $7AB0 (WHICH, IN TURN, CALLS
THE RWTS).  JUST BEFORE EACH OF THESE CALLS, THE IOB IS  SET  UP  WITH  THE
STARTING  TRACK/SECTOR, THE LOAD ADDRESS AND THE NUMBER OF SECTORS TO READ.
THE TRACK/SECTOR TABLE IS AT $65D0-$65F3.  HERE IS WHAT IT LOOKS LIKE:

              65D0:03 05 07 09 0C 0E 00 04
              65D8:08 0C 03 07 12 12 13 13
              65E0:14 15 00 08 03 0B 06 01
              65E8:16 16 16 16 16 16 00 02
              65F0:04 06 08 0A

THE FIRST 6 BYTES ARE THE TRACK NUMBERS FOR THE FIRST "FILE"  FOR  EACH  OF
THE  SIX  LEVELS.   THE NEXT SIX BYTES ARE THE CORRESPONDING SECTOR NUMBERS
FOR THE FIRST "FILE".  THE NEXT SET OF TWELVE  BYTES  ARE  FOR  THE  SECOND
"FILE"  AND  THE  THIRD  SET  IS  FOR  THE  LAST OF THE THREE "FILES".  FOR
EXAMPLE, WHEN YOU START THRESHOLD, YOU ARE AT LEVEL ONE.  THE 3 FILES START
AT T3-S0, T12-S0 AND T16-S0, RESPECTIVELY.  AT LEVEL TWO, THE 3 FILES START
AT T5-S4, T12-S8 AND T16-S2.  THE VALUES ABOVE ARE NOT WHAT YOU WILL SEE ON
YOUR  THRESHOLD DISK.  THEY ARE THE LOCATIONS I USED TO SAVE THE FILES ONTO
NORMAL DOS.  THE INTERPRETATION OF THE TABLE IS THE SAME, HOWEVER.

THE NUMBER OF SECTORS TO  READ  FOR  EACH  OF  THE  THREE  "FILES"  ARE  AT
LOCATIONS  $93A1,  $93C7 AND $93ED RESPECTIVELY.  THE TOTAL IS 240 SECTORS!
USE THE INSPECTOR TO READ IN EACH OF THE 18 (6 LEVELS * 3  FILES)  "FILES",
ONE  AT  A  TIME, AND THEN RE-BOOT NORMAL DOS AND WRITE THEM BACK OUT.  YOU
WILL HAVE TO USE A SECTOR EDITOR TO MODIFY THE VTOC  OF  YOUR  TARGET  DISK
BECAUSE  THEY WILL NOT EXIST AS NORMAL DOS FILES.  IN ORDER TO PREVENT THEM
FROM ACCIDENTAL ERASURE, YOU SHOULD FLAG THOSE SECTORS IN THE VTOC AS BEING
IN USE.  I FOUND DISK FIXER TO BE THE EASIEST FOR THIS PURPOSE.  YOU COULD,
OF COURSE, MAKE THESE NORMAL DOS FILES, BUT THEN YOU WOULD HAVE  TO  MODIFY
THE MAIN CODE TO READ FILES INSTEAD OF A SERIES OF SECTORS.  CHALK IT UP TO
LAZINESS ON MY PART COUPLED WITH THE FACT THAT THE PROGRAM RUNS  FASTER  IF
IT DOESN'T HAVE TO GO THRU THE DOS FILE MANAGER!

HOPE  THIS  HELPS.


                       ===  TRYSTAN  II  ===