Cannot run Megaman 9 NES demo

[maxoakland]

Summary of issue

Read https://github.com/OpenEmu/OpenEmu/wiki/Troubleshooting:-Reporting-problems

Steps to reproduce

1. Go to this website, download the game https://lukaszkur.itch.io/mm9
2. Try to run the game
3. It only shows a black screen
4. I believe it's because the Mapper isn't supported

Expected Behavior

1. The game should run correctly

Observed Behavior

1. Black Screen

Debugging Information

• OpenEmu Version: 2.3.3
• macOS Version: 10.14

[carmiker]

This ROM hits instruction SBX, which is an unofficial opcode. This brings us to three possible problems:

1. The instruction does not necessarily behave reliably on real hardware and documentation may not be 100% accurate
2. There is something wrong with banking in the emulator which causes the CPU to try to execute a part of the ROM that is not actually an instruction
3. The ROM was built against a specific emulator and/or SD cartridge and has not been thoroughly tested

This does not work on Nestopia, FCEUX, or Mednafen from quick testing. Working on an Everdrive does not confirm it works on real hardware -- this confirms that it runs on the Everdrive's implementation of the MMC5 mapper chip only.

Should it be proven that this is an emulation bug, I am happy to fix it. Until then, I will assume the demo has not had sufficient testing to determine factually whether this is an emulation bug.

[maxoakland]

Thank you for explaining that. I'll let the ROM maker know this

[carmiker]

@maxoakland this problem is fixed upstream now. It came down to stupid heuristics limiting the amount of exRAM + save RAM. It's a little late, but the next tagged release will fix this and other MMC5 hacks.

[maxoakland]

@maxoakland this problem is fixed upstream now. It came down to stupid heuristics limiting the amount of exRAM + save RAM. It's a little late, but the next tagged release will fix this and other MMC5 hacks.

That's awesome! I still want to play it