accumulator is then loaded with the error character placed in
$ClCB and compared to a $31. This is the hexadecimal
equivalent of a 21 error ($322, $31=1). Notice that if both
comparisons ARE equal, the accumulator is loaded with a 0, if
not, it's loaded with a 1, then a RTS.
J) Disassemble $C119 : The accumulator is compared with 0, and
if equal a branch to $C127 occurs. To see what happens, type
G C127 and hit RUN/STOP-RESTORE. Code was transferred to the
$8000 area of memory and was activated by the RUN/STOP -
RESTORE. You'll have to turn off the computer and reload the
monitor and the LOADER file again.
K) Disassemble $C11B : Increment $C1AB (increments the track of
the Block Read to 33).
L) Disassemble $C11E : Increment $C1AB (increment the sector of
the Block Read to 09).
M) Disassemble $C120 : JSR C14B : Goes back through the error
check routine once again but now the 21 error at Track 33,
Sector 9 is checked (the second drive rattle). This time if
the code is not branched to the message screen as before, it
will return back to $C01A to resume normal loading.
N) This program can be broken in many different ways. Three will
be given.
1) Place three NOPS at $C017 (EA EA EA). This will erase the
code that sends the program to the protection check in the
first place (our choice). The program will never do an
error check.
2) Place a BNE at $C119 and $C124 (D0). This will instruct
the program to operate in an opposite fashion in regards
to the protection, in other words, crash if an error is
found.
3) Place a $30 at $C162 and $C169. This will instruct the
program to expect NO error at the Block Read locations.
Again, if an error is found, the program will crash.
O) Choose one of the above methods and make your changes using
the MEMORY command. After the change is made the LOADER file
may be scratched and saved. Checking the disk log shows us
the start address of $C000 and the end address of $C2BC.
Remember to add one byte to the end address
<> S "@0:LOADER",08,C000,C2BD <>.
Your backup is now broken and will never rattle the drive again.
K.J. REVEALED TRILOGY PAGE [6] (C)1990 K.J.P.B.
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