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Hall of Fame
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HallofFameCDROM.cdr
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yeager.lzh
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YEAGER.PAT
Wrap
Text File
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1987-11-14
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2KB
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60 lines
How to Unprotect Chuck Yeager's
Advanced Flight Simulator
version 1.0
This program uses a rather simple protection scheme to prevent
you from making usable backups or installing it on a hard drive. The
program allows you to make as many copies as you want from the master,
however the master disk must be in drive A to use those copies. This
unprotect shows how to bypass that feature.
Because the program always looks to the master for verification,
I scanned the entire disk using Norton's NU program, and found track
15 was marked as BAD. After some investigation, it looks as though
that track was formatted as having over 100 sectors!! Unable to
reproduce that formatting scheme on my backup disk, I disassembled
the AFS.EXE file and found the following code (comments and labels are
mine):
E8 0B 00 CALL 0AB8 ; Check copy protect
3C 00 CMP AL,0 ; if al = 0 it's a master
74 06 JZ OK
BE 53 05 MOV SI,OFFSET 0553 ; else print "No key disk"
E9 0C A7 JMP BAD
OK: RET
As a fluke it tryed just NOP'ing the comparision code out, and
lo and behold it worked!! Total time to unprotect, 45 minutes.
How to unprotect:
1) Copy master disk using diskccopy. Do the following changes
on that copy, NOT the master (just in case).
2) Using Norton's NU or similar, in AFS.EXE, search for the
entire HEX string or smaller portions of:
EB 0B 00 3C 00 74 06 BE 53 05 E9 0C A7
3) Set the following HEX bytes to 00 (NOP):
3C 00 74 06 BE 53 05 E9 0C A7
4) Write changes and exit.
When AFS boots, it will no longer read drive A and may be copied
using DISKCOPY.
Another Hack from,
The Mole. :)