Posts for TheAlmightyGuru

Posted: 11/9/2021 7:12 PM
Post subject: Cheats from a technical standpoint
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TheAlmightyGuru
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Joined: 5/4/2012
Posts: 10
Is there anyone who can help me navigate the BizHawk source code and find where cheats are actually processed? I've found the code for the cheat dialog, but I'm more interested in how they're actually implemented when they change RAM, specifically for Z80-based machines like the Game Boy and Master System.
Posted: 10/6/2021 8:26 PM
Post subject: Unicode in Hex Editor
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TheAlmightyGuru
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Joined: 5/4/2012
Posts: 10
I love how the hex editor lets you load TBL files to be able to easily read text encoded in the ROM and search for text based on the loaded TBL file. Unfortunately, it seems FCEUX is limited to ANSI files and doesn't support Unicode. I recently created a TBL file for the game Dragon Ninja, which is mostly Japanese hiragana. I saved the file with UTF-8 encoding, but, when I load it in the hex editor, FCEUX treats it like and ANSI file and none of the Japanese kana are displayed. No doubt, because of this, I can't use the Find->Text feature either. Does anyone know if there is a setting I need to turn on to have FCEUX use UTF-8 TBL files? Or, perhaps a different encoding I need to use to get it to work? Thanks!
Posted: 12/12/2020 7:41 PM
Post subject: Re: Odyssey2 System Bus only shows ROM.
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TheAlmightyGuru
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Joined: 5/4/2012
Posts: 10
Alyosha wrote:
No, system bus is what is visible to the 8048 from the PC register, which in this case is just whatever ROM banks are currently mapped in and the BIOS. RAM, ppu, etc are accessed with port R/W functions. I guess I could make a separate 'port bus' domain but it would be kind of messy, and even that would miss CPU RAM which is internal to the cpu. So, I think in this case it's better just to use the individual domains.
Very interesting! I didn't know that about the Odyssey2. Thanks for the answer!
Posted: 12/12/2020 3:57 AM
Post subject: Odyssey2 System Bus only shows ROM.
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TheAlmightyGuru
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Joined: 5/4/2012
Posts: 10
The System Bus memory domain in the Hex Editor and RAM Search for the Odyssey2 emulator appears to only show the ROM memory domain. Is this a mistake? Shouldn't the system bus include the RAM?
Posted: 11/24/2020 9:43 PM
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TheAlmightyGuru
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Joined: 5/4/2012
Posts: 10
Now I've found something that I am confident is a bug: The cheat interface allows you to specify how you want your cheat values to be displayed (unsigned, signed, hex, or binary), and the cht file format has a column which saves this value which is represented as a u, s, h, or b. This way, it knows how to convert the number when it's loaded from the cht file. However, when you save your cheats, all of them are saved as type h, but the compare column is saved as the display type, which causes problem when the cheat file is reloaded. This problem only occurs when saving a cheat. If you manually alter the cht file to have the proper display type, it will load correctly. I tested this in version 2.5.2.
Posted: 10/21/2020 4:22 PM
Post subject: New cheat update
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TheAlmightyGuru
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Joined: 5/4/2012
Posts: 10
The NES Hacker Wiki has just been given a major cheat update. You can now download a collection of over 3,300 cheats across 300 games. http://www.thealmightyguru.com/Games/Hacking/Wiki/index.php?title=Cheat_Archive These can be very helpful for anyone trying to make a TAS since they include the addresses for a lot of values in memory. The cheats will work with various emulators, including FCEUX.
Posted: 10/21/2020 4:16 PM
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TheAlmightyGuru
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Joined: 5/4/2012
Posts: 10
For those who like playing around with NES cheats, the NES Hacker Wiki has just been given a major cheat update. There are now over 3,300 cheats spanning 300 games, and the cheats have been refactored to work with assorted emulators. http://www.thealmightyguru.com/Games/Hacking/Wiki/index.php?title=Cheat_Archive These can be very helpful for anyone trying to make a TAS since they include the addresses for a lot of values in memory. Unfortunately, because it doesn't support multiple cheats per address, a lot of them won't work properly BizHawk . Also, because BizHawk doesn't include region or version in their cheat file naming conventions, there might be some confusion as to which cheats will work and which won't as I mentioned above, but this is still a good start. If you use FCEUX, Nestopia, or the other supported emulators, they should all work correctly.
Posted: 10/12/2020 7:34 PM
Post subject: Can't add multiple cheats to the same address
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TheAlmightyGuru
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Joined: 5/4/2012
Posts: 10
This is another issue I discovered with BizHawk's cheat system and I don't know if I should classify as a bug or usability issue. You can only store a single cheat per memory address. How to reproduce the problem: 1.) Load the USA release of Little Nemo: The Dream Master. 2.) Open the Cheats dialog by going to Tools -> Cheats. 3.) Enter the following cheat, Name: Start on Stage 2, Address: CAB9, Value: 01, Compare: 00. 4.) Click Add and the cheat will be added to the list. 5.) You can test the cheat by doing a soft reset and starting the game. You will begin in stage 2. 6.) Enter the following cheat: Name: Start on Stage 3, Address: CAB9, Value: 02, Compare: 00. 7.) When you click Add, instead of the cheat being added to the list, it will overwrite the previous cheat. Why this happens: BizHawk uses address as a unique identifier and prevents multiple cheats from being added on the same address. Even if you add multiple cheats on the same address manually to a .CHT file, the moment you load them into BizHawk, only the last one in the list is added. Unfortunately, this makes it impossible to add multiple cheats to the same address, and there are several reasons for why you would want to have multiple cheats on the same address (though not active at the same time). In addition to having a cheat for each starting level, you might want multiple cheats on the same address for different weapons, to have different items in your inventory, etc. Potential Solutions: Work-Around: For every cheat you want to use that is on the same address as another, you can store it in a unique cheat file on disk. So, if you wanted to have a cheat in Super Mario Bros. for starting levels, you would need seven different cheat files. Fix: Stop using the address as a unique identifier. If it's being used as a unique id for the cheat, consider using the line number from the cheat file as a unique id. I've checked FCEUX and Mesen, and they both support the ability to store multiple cheats on the same address.
Posted: 10/8/2020 7:08 PM
Post subject: Not sure if this is classified as a bug or just a problem.
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TheAlmightyGuru
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Joined: 5/4/2012
Posts: 10
There is a problem with how cheats are stored across multiple versions of the same game in version 2.5.1. I'm not sure if it counts as a bug, but it definitely causes undesired behavior. How to reproduce the problem: 1.) Open the NTSC release of Little Nemo: The Dream Master in BizHawk 2.) Click Tools -> Cheats to open the Cheats dialog. 3.) In the Settings menu, activate "Always load cheats," and "Autosave cheats." 4.) Enter the following cheat, Name: Infinite Keys, Address: 008C, Value: 09, and click "Add." 5.) You can verify this cheat works by starting the game and seeing 9 keys. 6.) Close the Cheats dialog, and close BizHawk. The following file will be created: ".\NES\cheats\Little Nemo - The Dream Master.cht" 7.) Open BizHawk and load the PAL version of the game. 8.) Click Tools -> Cheats. 9.) The Infinite Keys cheat will appear in the list. 10.) Start the game, and notice that you start with 0 keys. Why this happens: When BizHawk auto saves the cheat file, and it was able to correctly identify the ROM, it uses the game's title as the name of the cheat file. However, it doesn't include the region in the cheat file name. The NTSC and PAL versions of Little Nemo: The Dream Master use different memory addresses for several variables, including keys. This is also true for a lot of games that have a different version for their Japanese/USA/Europe regions, as well as games with multiple revisions like Zelda, SMB3, etc. Because BizHawk doesn't distinguish between the different versions of the ROMs in the cheat file name, it doesn't store different cheat files for each unique ROM, and loads the same cheats for each ROM even though they won't work. Potential Solutions: Work-Around: Don't use autosave or autoload. You can still manually load and save your cheat files with a unique name, although, you probably won't know which regions are compatible and which aren't. Simple Fix: Always use the name of the loaded ROM file as the file name of the cheat file. This guarantees a unique file for every individual ROM. This solution should be easy to implement since the code is already written for ROMs that are not identified. This also has the benefit of consistency since all ROMs (identified or not) will function the same way. Alternate Fix: Include the region and revision number in the file name of the cheat file for identified ROMs. You could also add the ROM's hash to the end of the file, though this would make it harder to determine which cheat when to which ROM.
Posted: 7/31/2017 7:03 PM
Post subject: Turbo Start/Select?
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TheAlmightyGuru
Experienced Forum User
Joined: 5/4/2012
Posts: 10
Is there a way to make a turbo mode for the start and select buttons just like how it works for B and A?