Looking for a solution

[Saturn025]

Hi,
I've been attempting to hack Sega CD games in the past few weeks based on info I've gotten here, here and modifying info somewhat from this page, but keep running into a similar problem.

I wanted to make different codes for Soul Star and although I found what controls Shield and Energy levels, I can't trace them back to the green base codes that would tell me the actual ROM strings to edit my original ISO or BIN with.
The method here worked great when I hacked Infinite Lives, Infinite Missiles and a work in progress Infinite Bombs but not so much for Shields/Energy.
While looking for info on finding pointers pointing to pointers, most of the info was straight forward if a search in HEX @ 4bytes provided a hit. My problem is that the search comes up empty and my progress is halted.

In the pic, my EDI Address says it's the one I'm already using in my CE list. So how to trace that back as a pointer w/ no additional information? Using the Genesis how to that's linked above, I've subtracted by one about 20 times with no luck.



If interested in getting the codes quickly, I'm using Fusion 3.64
Here's what I've noted about Soul Star:
Exact value of energy on stage 1 at start is 86, max=223, 224 crashes game
The lowest energy will go is 18

Exact value of shields on stage 1 at start is 12, max=31, 32 crashes game
The lowest shields will go is 0
Shields appear to increase by 4 when a power up is collected

First enemy shot caused energy to drop to 78

Btw, I'm not looking to have the work done for me, just hoping an expert can help me get over this hurdle with a tried and true method I can add to my knowledge base-as Google searches have provided little for me. Thanks for looking

[Tony H]

If I remember correctly, you should be looking at the ESI address, not EDI. Then use Cheat Engine's Memory Viewer to find that address. I haven't done any Sega CD hacks in a long time, so can't remember for sure.

[Saturn025]

Thanks, above where I said I was using the genesis method from the link, I was using the ESI as shown in that guide, then subtracting one. After about 20 tries I gave up. This has me stumped and before Soul Star I was attempting to stop the avalanche on the snowboarding level of Cliffhanger. Same problem. I easily found the static code to keep it from advancing but its ESI address was useless as well. I deducted about 20 characters on that one too with no luck.
ESI minus one or two worked like a charm for my other hacks but they all had clear values to work off of. Number of lives, missiles, etc. Maybe it has something to do with the avalanche and shield/energy being represented by bars and I'm missing something.

Thanks for the help though!

[Tony H]

If you're saying that when you search your iso file for a string of numbers that you got from CE and you don't get any matches (in your iso), then you have a problem. If you're saying you changed some values in your iso and it didn't affect shields/energy, then it's just a matter of figuring out the 68000 assembly.

[Saturn025]

Yeah, that was totally it.

Add the ESI code 'as is' as an address, browse it in Memory, then search the ROM for the string & manipulate the preceding byte(s.)

Thanks again for the help. Will try the avalanche in Cliffhanger shortly


EDIT: Updated as how-to for ref

[Tony H]

If you're still having problems, can you post a screen shot of the CE memory viewer page.

[Saturn025]

Well, that one worked like a charm.

Some background:
Found the energy ESI code in SS and changed the preceding ROM byte to 00. That made the ship explode immediately upon entering stage 1. Tried some higher #s and stage 1 wouldn't even start. (lockup/crash)
Tried the 2nd bite preceding the original string w/ FF and that let it increase but not decrease-which is awesome. Now I'll look for the other code that fills the energy meter (defaults at a value less than 14 at start) and see if I can put it at full strength.

I also have the ROM string for shields but so far manipulation hasn't changed anything. They still reduce like always so that's why I'm going after full energy first.

I'll definitely post a pic if I hit another wall. Still need to try the avalanche.

EDIT: Found the energy display string but changing the preceding bytes to 00 keeps the energy from increasing/decreasing at all. Will try some other values later on. In-game, increasing the value of this visual bar manually doesn't increase it either via CE. Max is 13 or 14 and freezing it at either makes the number jump back and forth between 6 (it's current actual value) and 14 (maxed)

Is there a technique to looking for whichever value will max out a bar? I know trial and error of the values between 00 & FF would be a start but not looking forward to re-booting this game 255 times.

[Tony H]

I'm pretty sure I see what the problem is now (why you keep having trouble). When you use CE to find a string of numbers to search for in your iso file, the numbers you are changing in the iso file are actually 68000 assembly language instructions or operands. Completely different than RAM addresses.

What it boils down to, is how bad do you want to hack iso files? If you want to be more successful at iso file hacking, you'll need to learn some basic 68000 assembly. If you are okay with your current level of success, then it's probably not necessary to learn any 68k asm. I taught myself basic 68k assembly (with help from lots of people along the way), and I can tell you it's not terribly difficult, but does require some time and effort.

[Saturn025]

That's great info, thanks! I'm very interested, as hacking these is fun and a good way to kill time at work.
Any particular guides or links you would recommend?

[dlevere]

http://www.virtualdub.org/blog/pivot/entry.php?id=84

[Tony H]

Not really sure which 68k asm docs are good. Maybe someone else has some suggestions.

Here's a link to some notes I wrote about it. Might be useful...

http://gamehacking.org/vb/threads/46...-Assembly-Info

EDIT: Thanks dlevere

[Pyriel]

http://www.freescale.com/files/archi.../M68000PRM.pdf

I usually prefer to go straight to the horse's mouth. Although, the lack of index makes this document a little daunting.

My favorite thing about the Genesis was the processor's support for BCD types, which some games mysteriously used. I don't know if that was a trick of the compilers or if developers were consciously deciding that since max money is 9,999, they'd might as well use a 16-bit BCD value.

[Saturn025]

Do you have any idea what Mezmorize was using to find all the Invulnerability codes in this thread? Specifically, the Soul Star code at the bottom of this post

Can still get hit by some enemies on certain 360° stages so I wanted to isolate what's causing it and see if I can fix it. I've had to use separate searches on many items for the regular and 360° stages so maybe this is just another instance of that.

However, no clue what activates something like invulnerability.

EDIT: Avalanche hack worked like a charm in Cliffhanger, btw First time I've seen what's after that unnecessarily long stage.

[Tony H]

Do you have any idea what Mezmorize was using to find all the Invulnerability codes in this thread? Specifically, the Soul Star code at the bottom of this post

Not sure. Mez still comes to the site, so maybe he will see this. Or you can just send him a PM.