The cartridge connector has a signal called "CIRAM /CE" which is the on-NES-motherboard RAM chip select. Cartridges usually connect this to PPU /A13, per the wiki. If a cartridge has its own RAM and a developer does not want to use the on-board RAM, should the cartridge have a pull-up resistor so that this pin is not floating? I looked as some NES schematics which do not show a pull-up on the mainboard, but I do not know if those schematics were "official".