i'm missing something to be able to make NES cheat

[panda]

I sent a message that will probably appear soon (my messages must be validated by moderator, probably because i'm still a new user here). No problem about it, that's fine, but i just wanted to add something, so here it is (at the time i write this message, i don't know if both of my messages will be validate in a way that will makes both of them to appear like 2 consecutive messages, i'm sorry if this happens, i would have prefered to edit my previous message if i could):

Anyway, i wanted to say that since "that" previous message, i've just read the new message from Hybrid.
And it made me realised that i was wrong in my message;; the code APSUELEI really works.

At first, i was thinking this cheat code was forcing the game to play at Easy Mode, and it was not doing that, so i used to think the code didn't work. But now i found that this cheat is used to actually add an invisible option to recover the possibility to select the Easy Mode. It's even better than my cheat 064C:00 that used to force the game to always play in the Easy Mode. APSUELEI can be activate all the time, while 064C:00 had to be deactivate to select the other difficulty, and re-active to play easy mode. My cheat was less convenient. Anyway, i confirm, both codes APSUELEI & LEXNGIZA works. Thanks for these 2 codes. I wish that i was able to make some cheat like these.

Well, if i knew how to hack a rom, i would modify the menu in the game to always have these options visible and making these options no more invisible, but i don't have the knowledge, i'm still trying to understand how to make Game Genie codes ^^

[Hybrid]

heres something that makes the player to mode b selectable as for the difficuly rimsky's code works fine as far as i can see (any enemies still on screen when you change difficulty retain their original difficulty)
2 player mode b selectable
LEXNGIZA

scroll down 1 past 2 player game your cursor will disappear

[panda]

The cheat APSUELEI doesn't seem to work. I tried new game on advanced difficulty and activate the cheat APSUELEI, but the ennemis were still playing on advanced mode. I also notice that with the cheat activated, it was still possible to select the difficulty level, while it is impossible to choose a difficulty when 064C:00 is an active cheat. If i start a new game on advanced mode, and after that i activate the cheat 064C:00 i can notice the game difficulty decrease.

I also tried to do something, but i think i fail somewhere because i never touched the Debugger before, but i want to learn, so i wanted to try it.

First things i have done is open the game, then, open the debugger and search for 064C, just like this:


Then, i double click on it to add breakpoint i activated "Write" and i added 00 because the value of the cheat is 00, it was what it looks like at that point:


But the game never seems to break or to freeze, even when selecting the difficulty level, so i tried to ask the debugger to "break when it exceed 0", and it pointed me directly to a new address and value:


So i tried to enter this new address and value FC73 D0 FE in fceux, and i got a Game Genie code VYNYUGES, but it only makes the game freeze, this cheat is not good:

[rimsky82]

So you know, I was able to make level 0 selectable with the code APSUELEI. However, the game doesn't care and friendly fire still exists. I'm not sure if the game is any easier or not.

[rimsky82]

You found the area in RAM where the value is stored, that's a good start. Now you need to use the debugger to figure out how to manipulate the ROM, the game's code, to write 0 to that address.

Set a write breakpoint on that address (064C) and restart the game. When you select the difficulty and start a new game, eventually the debugger will stop the game and show you the instruction that writes the value to that address. If you can manipulate the code around that instruction to write a 0 instead of 1 or 2, you'll have your code.

To make the final genie code, you'll need the address, value, and compare (the original value). Then you can use the tool in fceux or the page here to encode it to a genie code.

I will attempt to find a way myself, but I'm curious to see what you can come up with on your own. Also, the code to select the easy mode may still exist but be unused. That kind of code making is fun as well, to add missing functionality to a game. I did this by finding the gas tank in Top Gear 2 for SNES.

[panda]

Thanks for the reply. In the Japanese version of River City Ransom, called Downtown Nekketsu Monogatari, there was a choice of 3 difficulty (Easy, Normal, and Difficult). In River City Ransom, they removed the possibility to select the Easy mode. They renamed Normal to Novice, and Difficult to Advanced, but there's no equivalent to play the Easy mode. With Cheat Engine i found the value that was choosing the difficulty. And if i lock the value to 0, it force the game to play the Easy mode even if i can't select this difficulty in the game. So it's basically a code to restore something that was in the original game. It's not as good as having a patch version of River City Ransom where this possibility would be restored, but creating patch is beyond my knowledge and i think it's still an interesting code that allow the player to play in a mode that should have been included in the game. Just like the Game Genie code EYSEYAEI i found on internet, that one was to force the game to play in the multiplayer "Game B" Mode, a mode that allow the 2 players to avoid hitting each others, that was removed from the River City Ransom game too.

Today i tried to use the fceux Tools>Cheat to do the same thing that i was able to do with Cheat Engine, and as a result, i just found that the code i want to make is Address: 064C Value: 00. However, i'm unable to convert it to Game Genie code, and i wish i was able to understand better this part. It's quite strange that i can use Cheat Engine or fceux to create cheat quite easily, but unable to convert it to actual Game Genie cheat code. So when i use Cheat Engine, it seems i can't do anything with my result as i can't convert it, and when i use fceux Tools>Cheat, i can use it but it's still not a Game Genie code.

[rimsky82]

In your calculation, you are mixing addresses and values together. The Game genie cheat you found, with the decoded address provided by fceux, is relative to the NES' own CPU memory. Your cheat engine address is relative to your computer's RAM.

In addition, you likely found the RAM equivalent with cheat engine, which in the NES is a different address in a different memory space. So if you know the starting address of NES' cpu memory in your RAM, you can subtract it from the address you found to find the NES RAM address. Once you close and restart your emulator, the addresses will change.

It's easier to start at the beginning and guide you through. What is the code you are trying to make?

[panda]

hello.
i'm having a problem to understand how to make nintendo NES codes.
i found on internet a cheat code EYSEYAEI for River City Ransom and it works fine in game.
in FCEUX emulator, this cheat is: Address: 805F Compare: D0 Value: F0.
so i tried to find the same with Cheat Engine, and i found the RAW address was 00DF00B0 with a value of 2 to active the same cheat.

with this information in hand, i tried to make a new cheat, and i found with Cheat Engine the RAW address i was looking for my new cheat is:
00DF06C4 with a value of 0 to activate the cheat.

to convert my new cheat, i made these calculations (and i'm sure it's where i fail): 00DF00B0 - 805FD0 = 5EA0E0 + 00DF06C4 = 13DA7A4
weird result, so i tried 805FD0F0 - 00DF00B0 = 7F80D040 + 00DF06C4 = 805FD704 and it looks more like a real code.
i tried to enter my new code in FCEUX like this: Address: 805F Compare: D7 Value: 00 (i replace 04 by 00 because the value must be to 0 for the cheat to work). the cheat do nothing. i can't figure out what is my mistake?