The algorithm for decoding the address of an 8-character code is the same as decoding the address for a 6-character code. Instead, when the CPU reads from the cartridge, the Game Genie checks if the address in the cartridge equals the compare value and returns the code data value if it does otherwise, it returns the real value in the cartridge. Since the game might be swapping program (PRG) banks in and out of the CPU address space, the Game Genie can't just return the code data value when the CPU reads from a particular address. This is most likely due to the fact that many games use memory mappers in order to increase the amount of code and data they can use. 8-Character Codes 8-character NES Game Genie codes are similar to the 6-character variety except that there is also a compare byte value that needs to be decoded as well.
Therefore, whenever the CPU reads from address 0xD1DD, the Game Genie will intercept the read and return the byte 0x14.
Work through the code by hand to see if understand the decoding algorithm. This works in Capcom's Ghosts 'n Goblins to start your player with a really funky weapon. Here is the data algorithm:Įxample: The code is GOSSIP (amazing coincidence that it happens to also be an English word). The algorithm simply combines the lower 3 bits from one 4-bit nibble and the top bit from another nibble and puts the resulting nibble somewhere else. Follow the pseudocode (which assumes you know the C-style operaters for bitwise AND (&), bitwise OR ( ), and the > bit shift operators): In order to decode the 6-character NES Game Genie code, name the 6 characters/hex values. After all, given 2 Game Genie codes, one that granted 5 lives on startup and another code that granted 9 lives, and the only difference between the 2 codes was one character, even a novice player could probably figure out that modifying that one character to any of the acceptable letter characters would grant between 1 and 16 lives on startup. This is probably to make the Game Genie codes seem more magical. There is a lot of convoluted bit shifting that occurs in order to get the address and data from a Game Genie. To decode an NES Game Genie code, first translate each character into its hexadecimal equivalent using the following table: When the CPU attempts to read the memory address specified by the Game Genie code, the Game Genie apparently intercepts the read and substitutes the byte from the Game Genie code in place of the actual ROM byte. The address is 15-bit because address bit 15 is always set to 1 in order to reference the top half of the CPU address space. 6-Character Codes 6-character NES Game Genie codes translate into a 15-bit (not 16-bit) address and an 8-bit data byte. Because of this method, there is no limit to the number of Game Genie codes that can be discovered. The codes translate into addresses and data in a game's program space (upper half of address space, 0x8000-0xFFFF) which the Game Genie fools the CPU into using rather than the byte which is supposed to be there. The codes come in two flavors: 6- and 8- character. The Game Genie then allows the player to enter a code which consists entirely of letters. The NES Game Genie works by allowing the player to plug an NES game cartridge into it and then plug the Game Genie into the NES console in place of the cartridge. Get the best selection of Rygar: The Battle of Argus Cheats, Codes & Walkthrough/Guide/FAQ for Nintendo Wii from Cheat Code Central. The Genie has more Rygar: The Battle of Argus Cheats at. Nintendo Game Genie codes and stuff (the technical / 'how to' docs are at the bottom) Click on the game that you want original Game Genie codes for: Advanced Dungeons & Dragons: Heros of the Lance Adventure Island Attack of the Killer Tomatoes B-Wings Battle of Olympus Bio Force Ape (J) (prototype) California Games Castlevania 3. The best place to get cheats, codes, cheat codes, walkthrough, guide, FAQ, unlockables, tricks, and secrets for PlayStation 2 (PS2). AANT-CAGY+AAPA-CAB8 - Become Super-Duper Sonic without any emeralds(you still need 50 rings unless using one of the above codes) 37. This page contains a list of cheats, codes, Easter eggs, tips, and other secrets for Rygar for NES.If you've discovered a cheat you'd like to add to the page, or have a correction, please click. The NES Game Genie from Galoob is a device that allows a player to enter a variety of codes into a Nintendo Entertainment System game in order to cause the game to do things it would not normally do, e.g., grant the player extra (or fewer) lives at startup, give the player extra items, change the gameplay, or just cause crazy things to happen. With thanks to Cheatmaster for helping me figure out the NES Game Genie codes.