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-   -   Newbie hacking Questions (http://www.zophar.net/forums/showthread.php?t=8531)

larienna 04-23-2007 12:35 AM

Newbie hacking Questions
 
HI

I want to make a simple hack of "Super Conflict" on the SNES which will only consist in changing the stats of the units to re-balance the game. I don't know much about rom hacking and I don't know the best software available.

First, I tried to use an hex editor and I used a relative search tool in order to try finding a group of 3 stats that could be the stats of an unit. I made the modifications and tested the ROM but I got an CRC Check failure. So I imagine I need an hex editor that can change the CRC of the ROM?

Besides relative search, is there other methods that can be used to know where the information is located in the rom?

If I have a value that exceed 256. For example 2000. How is the value is generally store in the rom. Does the Value is separated in 2 bytes, high byte first, and low byte second or it's the opposite?

Is there a huge difference between NES and SNES hacking?

If you have any software suggestions that I should use to do the work, just tell me.

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KingMike 04-23-2007 03:25 PM

Re: Newbie hacking Questions
 
You can generally ignore the CRC Check, since the modified game is clearly not the same as a real cart (detecting whether or not a ROM is an exact copy of a cart is really the only point of a CRC).

SNES games typically store the low byte first.
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larienna 04-24-2007 10:27 PM

Re: Newbie hacking Questions
 
> You can generally ignore the CRC Check, since the modified
> game is clearly not the same as a real cart (detecting
> whether or not a ROM is an exact copy of a cart is really
> the only point of a CRC).

But the problem is that I cannot test the Rom in ZSNES if the Checksum fail.
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KingMike 04-26-2007 03:39 PM

Re: Newbie hacking Questions
 
> But the problem is that I cannot test the Rom in ZSNES if
> the Checksum fail.
>
Sorry, I'm not really sure what to say on that.
I tried it in ZSNES, changing a few random bytes at the end of the ROM, and it still loaded.
Not being familiar with the game, it's hard to say wether the data you change is correct, if some code is being corrupted.
(admittably, I'm using an old version of ZSNES, but I don't think it's ever enforced proper checksums)
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RaiBlastoise 04-29-2007 11:01 AM

Re: Newbie hacking Questions
 
I belive i heard about a program once where, if you were to specify an offset range where there was no game data (and as such it would be useless if one modified the data there), you could tell the program that range and the desired checksum, and it would alter the bytes to provide the desired checksum.

Hmm... now that I say that, it seems a bit far-fetched. Am I correct, confused, or just talking out of my behind after 21 hours sans sleep?

Anyway, good luck in your pursuits.
--Kitsune Taiyal

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Ugly Joe 04-29-2007 05:59 PM

Re: Newbie hacking Questions
 
> you could tell the program that range and the desired
> checksum, and it would alter the bytes to provide the
> desired checksum.

IIRC, there isn't really such a thing as a "desired" checksum. There's the actual checksum of the rom + header, and there's the checksum that is reported in the rom's header. All you have to do is figure out the checksum of the rom + header, and then put that checksum value in the header (along with some offset byte to keep the checksum value in the header from changing the rom + header's checksum <img src=smilies/retard.gif>).

There are definitely tools out there that will do all this for you.

However, I have to echo KingMike's response in saying that the checksum doesn't really matter. An snes emulator will alert you that the checksum is incorrect (as it's an indicator that your rom might be corrupt), but that won't stop the game from loading. It sounds like some important data was modified
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