Flashcarts don't work unless you devote the entire flash to a single ROM (some of them can do this). This is because the console snarfs the entire contents of the ROM into RAM first, rather than mapping the ROM directly into the CPU's memory space like the original consoles did. So the bank-switching tricks that flashcarts use to provide multiple ROM options on original hardware don't work on these. This is also why the 2600+'s pack-in multicart has a janky, DIP-switch solution to select a game.
Many large carts (8K and larger) also don't work, at least not without the firmware knowing how to bankswitch to read the whole ROM, so a fw update may be required.
> This is because the console snarfs the entire contents of the ROM into RAM first
The console itself should never know the cart is not a simple ROM with some bank-switching logic. Since Flash (or an SD card) isn't ROM, the ROM image will always be loaded into the cartridge RAM by the microcontroller software. There were many different strategies back then, so the ROM would need to have a file attached telling the on-cartridge microcontroller how bank switching worked on that title.
All you'd need is some UI to make it easier to switch between titles.
Most flashcarts have a UI that is shown on first boot; when a game is selected, the ROM for that game is loaded into the flashcart RAM, the appropriate bank switching or mapping logic emulated, the ROM banks remapped into the console address space replacing the UI code, and the console reset or told to jump to boot the game.
This doesn't work on the Atari 2600+ and 7800+ because those systems attempt to load the entire game ROM into their own RAM on boot and run the game from there. You might get the UI, but unlike in the actual hardware there is no rereading of the ROM directly. It's all done from what the system captured into RAM on first boot. So if a new game were to be loaded into that address space, the modern console wouldn't see it.
The boot menu uses some form of bank switching to get to the actual game ROMs and their specific switching strategy, if any. The 2600+ and 7800+ would need to know the method (a write to a specific address, perhaps) to get to the specific part of the ROM on a bank-switched game anyway.
I never tried that, so I might be very wrong in my assumptions.
In the case of the imaginary cartridge with the UI, changing the ROM that’s mapped to the cartridge space with the physical UI and resetting the console without resetting the card controller should do the trick.
The bank switching mechanisms in all commercially released games can be enumerated and emulated by the 2600+, but I think they just haven't gotten around to updating the firmware. Many bank-switched commercial games still don't work afaik.
Flashcarts are more of a crapshoot. They use unknown bank switching mechanisms and Atari does not want to support their use.
> In the case of the imaginary cartridge with the UI...
Not so imaginary! This is what the pack-in cart that comes with the 2600+ does, there are DIP switches for game selection on the cart itself. I don't know of any flashcarts that do even this, let alone something more sophisticated with buttons and an LCD readout like a Gotek drive emulator or something. Would be nice though...
