I know this isn't exactly the right web site, but...
As far as I can tell, it should not only be possible, but, in fact, easy, to make an image that, when actually in a Genesis, could boot either in Master System mode or in Megadrive modeāThe Genesis requires a specific value at addresses that are disjoint (I think!) from the required values for the Master System. And the Genesis uses a full 16-bit wide data bus, while the SMS only uses half of it (D8-D15 seem to be unused)
So the question is: does it already exist? Has someone already designed the software that would run on a physical cartridge that you could put into a rev1/rev2 Genesis and have it successfully do a thing regardless of whether the /M3 pin is floating (Genesis) or tied to ground (SMS) ?
As far as I can tell, it should not only be possible, but, in fact, easy, to make an image that, when actually in a Genesis, could boot either in Master System mode or in Megadrive modeāThe Genesis requires a specific value at addresses that are disjoint (I think!) from the required values for the Master System. And the Genesis uses a full 16-bit wide data bus, while the SMS only uses half of it (D8-D15 seem to be unused)
So the question is: does it already exist? Has someone already designed the software that would run on a physical cartridge that you could put into a rev1/rev2 Genesis and have it successfully do a thing regardless of whether the /M3 pin is floating (Genesis) or tied to ground (SMS) ?