You can see this on many consoles, iirc it basically just boils down to some address pins not being connected anywhere, so whatever the pins are set to doesn't matter as they're just out in the air so to say.
You can see this on many consoles, iirc it basically just boils down to some address pins not being connected anywhere, so whatever the pins are set to doesn't matter as they're just out in the air so to say.
Then there’s the opposite situation. I knew the guys who ported NBA Jam: TE from arcade to PC (by hand-translating assembly!). Apparently the arcade CPU had bitwise addressing. And, because pretty much all of the data was aligned to bytes, the arcade programmers liked to stuff 3 bits of extra parameter data into the low bits of pointers.
You could do that on PC too, if you mmap() one given block of memory at multiple locations. I think that's how PS1 emulators handle mirroring (it's been a long time since I took a peek at the innards of DuckStation).
ha! I wish I knew this back then, but now I do remember - I think what we did was simply clearing the bit before access, and it was in just dozen or so places. Slap a macro and you are done!