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Methods of searching for codes

 
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LitCandle
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Joined: 28 May 2008
Posts: 60
Location: NS, Canada

PostPosted: Mon Aug 25, 2008 12:16 am    Post subject: Methods of searching for codes Reply with quote

I'd like to know how to use dissasembly to find codes (to backtrack to locations that write potions and stats in Dungeon Explorer, and money in Moto Roader)

the way I search for codes is I use Cheat Engine, then translate the codes into magic engine's cheat system. (I also use it for old DOS games, and every other kind of game too - but haven't shared the addresses since cheat engine addresses change as the program changes, you need to find the addresses for the cheat system in the emulator if you want to keep the same codes forever)

1. start pce.exe (it helps to run pce in a window the entire time you're searching for cheats for switching between windows)
2. load the pce.exe process in Cheat Engine
3. search

I like it because there's more search options for searching for cheats than the ones built into magic engine, and you can search through the complete address range in the emulator (ie. finding CD games cheats and others magic engine doesn't know about). I don't know how to disassemble and backtrack through assembly to find cheats yet but you can do that too in Cheat Engine

Finding cheats for CD games with wierd addresses:

this is as easy as finding cheats for normal games, the *very* difficult part is translating them back into magic engine (since you neither can find the address in magic engine nor search for it in the magic engine cheat system) so here's how I do it by trial and error (this is hard to explain but this is what I do step by step):

Step 1, find your cheat

Step 2, finding what address in Cheat Engine corresponds to F82000 in magic engine.... I go in the magic engine cheat menu and change the value at address F82000 to 12, then I go in Cheat Engine and search for 12, then go back into magic engine and change that value to 13, then go back into cheat engine and continue search for 13, if there's only one address left, I've found what F82000 corresponds to in Cheat Engine (something like D836000 in my case)

Step 3, finding what address your cheat at a wierd address corresponds to in magic engine by trial and error (the hard part).... say for example your cheat is at D846000 (in my case), this doesn't fit in the F8xxxx series cheat or the CD RAM address cheats, but.. it does fit in the cheat tree somewhere. What we need to do is change values in magic engine at random addresses (scanning all possible addresses in the magic engine cheat system - from 000000 to FFFFFF) and see what they correspond to in Cheat Engine until we find the address that corresponds to D846000 (in my case) and this can take a long time and you will feel like giving up several times until you find it
1. Open up notepad or wordpad because you're going to use it extensively
2. write this in notepad D836000 = F82000
3. repeat Step 2 (not 2. (one line above this one)) to find out what address in Cheat Engine corresponds to (this time) F84000 in magic engine and start a new line in notepad and write down D838000 = F84000
4. keep repeating 3. for all addresses in magic engine until you get closer and closer and finally find what address = D846000 in the magic engine cheat system
Here's what I've tried to make my searching faster:
1. only search xxx000 (ie. the first 3 digits of your cheat) since the last 3 digits are the same when you finally find the address
2. try F82000, F84000, F8A000, F8x etc. (always write D83x000 = F8x000 in notepad - you need to record everything to clue into what's going on and the patterns)
3. try F92000, F96000 series
4. FA series, give up and try other series starting away from F
5. 000000, 003000, 010000, 013000
6. 110000, 113000, 150000, 153000
7. 210000, 213000, 250000, 253000, etc.
8. in these wierd addresses, the same value is repeated at several addresses, once you find the pattern (say 212000 = 214000 = 216000) you can avoid searching those even number addresses that hold the same value and look for odd addresses, in some cases it's multiple addresses in a row

LitCandle
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lexluthermiester
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Joined: 18 Feb 2008
Posts: 32

PostPosted: Mon Aug 25, 2008 3:41 pm    Post subject: Reply with quote

In reference to the difficulty of find codes for games with "weird" addressing schemes; wouldn't it be easier to simply figure out where MagicEngine stores the emulated ram addresses for the Super CD cards? The way the System CD cards worked is that they had extra ram on them[in various sizes] and the cd games store extra info directly on them. So finding the address range MagicEngine uses for these cards should be the key to finding codes for cd games.

Please someone tell me if I'm wrong...
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LitCandle
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Location: NS, Canada

PostPosted: Mon Aug 25, 2008 5:49 pm    Post subject: Reply with quote

dmichel explains it in this post

LitCandle
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Kaminari
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Joined: 19 Apr 2002
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Location: Paris, France

PostPosted: Tue Aug 26, 2008 7:56 am    Post subject: Reply with quote

lexluthermiester wrote:
The way the System CD cards worked is that they had extra ram on them [in various sizes]


That's only true for the System Card 3 and the Arcade Card. Previous System Cards didn't have any onboard RAM and were limited to the standard memory of the PC Engine (64 kB if I remember correctly).
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