Since the PRG RAM and the CHR RAM are both 8kb, was there any mapper that let you bankswitch the two?
To be clear, not separately like most of them, but with each other. Switch the tiles to cpu-writable space, write them even during rendering, switch back to CHR.
To be clear, not separately like most of them, but with each other. Switch the tiles to cpu-writable space, write them even during rendering, switch back to CHR.