@pichichi010: The carts containing only LoROM games write a specific value on the 0xffff00-0xffffff memory range to determine which 512k/1M/2M bank inside the 8M file has to be loaded in [00-7d][8000-ffff] memory ranges (as LoROM). Once this has been done, memory remains the same until you reset or turn off the console
The carts containing both LoROM and HiROM games (at least one apparently exists) are thought to also write a bit to determine if the game has to be mapped as Lo or Hi. This is only theory, though, because the HiROM game in the existing dump is missing so there is no way to confirm this assumption.
more info at:
http://nocash.emubase.de/fullsnes.htm#snescartpiratexin1multicartsbasically, the only way for these to work on an emulator, is to have the emu author adding support for these writes at 0xffff00-0xffffff, which are otherwise just interpreted as writes to WRAM and have no bankswitch effect
@Azathoth: the 6-in-1 game depicted in the images above is the *only* multigame cart fully dumped, to my knowledge (+ the korean 20-in-1 dumped by d4s last year).
Other carts dumped but with incomplete dumps are the following (I put here snaps because I'm too lazy to write down the game names)
about dumping, the best way would be to open the cart and read the chips with an EEPROM reader, because I have no idea which modifications would be needed by a Retrode to access the whole data...