@chrisbati

Unfortunately, c64 and spectrum joysticks only had one fire button command, no matter how many physical buttons there were.

The adapter may support more buttons on the output, but if it has no difference in the incoming signal, it won't be able to do anything else.

@spruce_m00se for using tons of db9 controllers i recommend either a vision-daptor or ultimate pc interface (upci is 2player version. Has some other controllers the vision-adapter doesnt have. Both made by the same person.) The master system also has the two extra pins as functiong buttons. They match the same button numbers as start and mode button on the genesis mode. He added these so i could use my db9 modified nes and turbografx/pc engine controllers. He makes some other controller adapters too. His adapters truly are the best i have ever used.

I see. So the Xbox dongle would in port 0, the nes in port 1, the DB9 connectors (if this works) in port 2, and the "rom drive" in port 3. Now, what about using a USB hub? I bought a 4-port hub to connect USB devices to (like keyboard, mouse, etc) via the cartridge slot. Should this be plugged into 0, and then the Xbox dongle plugged into that? Or would it make more sense to connect the rom drive to that and have it plugged into port 3? I found out the 4-port (usb powered) hub isn't powerful enough to supply power to my keyboard, so I'm going to the computer store tomorrow to buy a powered one, and was thinking a 7 port one would work nice. The kind with 4 on one side (available via the cartridge slot) and 3 "internal" that I can connect things like the NES ports too. I'm just trying to figure out the best way to do it.

So is at all possible then the idea of having interchangeable controllers?

using /etc/module for module options has been deprecated for some time, but worked in Raspbian Wheezy. Now it doesn't - the wiki needs updating in this area - feel free :-)