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Old 01-05-2013, 04:29 PM   #1
Dream Weaver
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Question A daft question about ROM-hacking?

Hi all!


Apologies if this is a daft question, but here goes... Iím a complete noob, see, and want to get into some serious SNES-based ROM hacking. Iím reading and re-reading as much as I can on the subject, and eventually itíll all start to pay off and make some sense, but until such time, my question is this: if I want to create a ROM hack or ROM-hacking tool for a particular game, say SMB3 on All-Stars, while Iím still trying to get my head around the basics of ROM-hacking, is there much point in me spending time using the ZSNES cheat-finder to map (relevant bits of) the RAM, eg Map pointers for Stages?
In other words, with the right tools and skills some time in the future, would I be able to use the RAM data Iíve accumulated to locate the bits of ROM that point to it?

Obviously a basic familiarity with the RAM would be useful in a general sense, but I mean more in terms of reverse engineering from the RAM directly to the appropriate bits of ROM, so to put it (yet) another way:

On SMB3 the RAM pointers for enemies within a stage are in consecutive groups of 3, like so:

7E1B41XX = enemy select (for enemy #1)
7E1B42XX = x-axis start coordinate (for enemy #1)
7E1B43XX = y-axis start coordinate (for enemy #1)

With this information, and knowing the particular hex values for enemy #1 within a given stage, could I enter said stage, and then use a tool to see which ROM is (currently) pointing to this RAM, and if the enemy was, say, a ďDry BonesĒ, thereby find out where the ROM for Dry Bones is...??? (Or, at the very least, find out the ROM address that selects this enemy as Dry Bones, and thereby edit said ROM address to change it to a Ghost, Thwomp, et cetera?)

As I say, sorry if this is a daft question, but it would be good to know if I can get on and do something useful while I read up on Ďproperí ROM hacking...

Cheers!

Gethin
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Old 01-06-2013, 05:18 PM   #2
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RAM locations can be converted into ROM locations. I've never really dealt with it much but I've seen discussions of how to convert from one to the other. I believe SNES is a bit more complicated than other older consoles because of the way it handles memory, but it's definitely doable.
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Old 01-06-2013, 11:18 PM   #3
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Ta very much, InVerse...! Much obliged. That gives me something constructive to do while I try and learn ROM-hacking.

One more question, if you don't mind; given what you said, would you say it's worth me writing up a few RAM maps for SNES games, and posting them on sites like this (with the proviso that it's not stuff that's already all over the web, on various hacking sites)?

Cheers!

Gethin
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Old 01-07-2013, 01:18 PM   #4
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DataCrystal has a section for RAM maps. I wouldn't bother posting ANYTHING on Zophar's Domain. The only reason people still submit stuff here is because of the high search engine ranking. People who actually know what they're doing and would know how to use the data are just going to go straight to DataCrystal first.
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Old 01-11-2013, 09:08 PM   #5
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Ah OK. Thanks for that, InVerse. That's good to know.
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Old 01-11-2013, 09:46 PM   #6
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Just had a quick looky on Data Crystal, and remember that place from a number of futile Google searches (looked promising but no joy on what I was actually searching for). Think I'll just post a few docs on here anyways...

Thanks for the tip though...
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