MERCS © CAPCOM/USGOLD 1991
Original game – find on emunova.net
An Amiga or WINUAE
Action Replay or ROM image
Pencil and paper
X-copy to create a copy from which we will work
An easy crack to do….. just have 2 minutes for you and it’s ok 😀 Start with making a copy of the original game disk. You’ll notice an error on track 79.
Plus when looking on track 0 the bootblock, you’ll see that the game use an allocation file table. This means the game files are coded on the disk, a bit in the same vein as Black tiger From the same Publisher.
Ok, reset your Amiga, and boot the game :
When you’re on this screen, check when the loader counter stop on track 5, and activate action replay III I have found the copy protection routine. It uses a sync of $4124 and the length to get to pass the track is $1900.
Right below the beginning of the prtection routine : 3BC : The registers are saved on the stack 3C0 : Branch sub routine at 636 3C4 : Test that WORD in D04 is equal to 0 3CA: Be not equal then branch to 452 This is where we strike right away, we will change the instruction 3CA by replacing the BNE by a BEQ.
The game check first that word in address D04 is equal to 0 or it launch the protected track check Right away. So we need to make it know that everything’s fine 😀 Ok now we get the string in order to replace the thing :
M 3C0
You’ll get this : 61 00 02 74 4A 79 00 00 0D 04 66 Once modified : 61 00 02 74 4A 79 00 00 0D 04 67 Now, let read the bootblock :
RT 0 1 70000
Now search for the previous string :
F 61 00 02 74 4A, 70000
It should return you the address 706C0.
The address to modify on disk is 706CA :
A 706CA
706CA BEQ 70752 There’s no need to recalculate the checksum, So write back on disk :
WT 0 1 70000
Reboot your amiga or Winuae and run the fucking game : It works like a charm !!!
DLFRSILVER in march 2009 Cheers to Musashi9, Stingray, WayneKerr, Galahad, Codetapper, and ROB!
Played to the end so it’s 100 % Have fun with this slow game and straight ATARI ST code port !