MERCS
© CAPCOM/USGOLD
1991

   1. Original game – find on emunova.net
   2. An Amiga or WINUAE
   3. Action Replay or ROM image
   4. Pencil and paper
   5.  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 !


Subscribe
Notify of
guest

0 Comments
Inline Feedbacks
View all comments
0
Would love your thoughts, please comment.x
()
x