I don't know how the Polymega works, but for the example the Hyperkin Retron or the Atari 2600+ are "DOM Dumpers": You put in the cartridge, the system dumps the EEPROMs to RAM, and then plays them.
The issue is that if you have a cartridge with any custom chips in it, they won't work because the software doesn't actually connect the cartridge to the emulated system. It's possible to built in heuristics to detect a known game (e.g., if I detect Pitfall 2 on the 2600, I can tell the emulator to emulate the video/sound chip on the cartridge), but if I have a homebrew cartridge, I'm out of luck.
This is especially common on NES and SNES games, there were so many custom chips around, some used on only 1 game (e.g., the DSP2 chip on SNES Dungeon Master), though other consoles also occasionally used it (like Virtua Racer on the Genesis, or as mentioned, Pitfall 2 on the Atari 2600).
With a hardware-based emulation, it's possible to electrically connect the cartridge to the system and achieve full compatibility (assuming the hardware emulation is correct), but there's AFAIK no software emulator that can be fully coupled to a cartridge connector.
So, not sure what would happen if I grab a SNES cartridge with a DSP2 chip (aka. Dungeon Master) and flash my own EEPROM onto the game - would the Polymega work for that or not?
The issue is that if you have a cartridge with any custom chips in it, they won't work because the software doesn't actually connect the cartridge to the emulated system. It's possible to built in heuristics to detect a known game (e.g., if I detect Pitfall 2 on the 2600, I can tell the emulator to emulate the video/sound chip on the cartridge), but if I have a homebrew cartridge, I'm out of luck.
This is especially common on NES and SNES games, there were so many custom chips around, some used on only 1 game (e.g., the DSP2 chip on SNES Dungeon Master), though other consoles also occasionally used it (like Virtua Racer on the Genesis, or as mentioned, Pitfall 2 on the Atari 2600).
With a hardware-based emulation, it's possible to electrically connect the cartridge to the system and achieve full compatibility (assuming the hardware emulation is correct), but there's AFAIK no software emulator that can be fully coupled to a cartridge connector.
So, not sure what would happen if I grab a SNES cartridge with a DSP2 chip (aka. Dungeon Master) and flash my own EEPROM onto the game - would the Polymega work for that or not?