What EPROMs should I use to make my own NES cartridges?

Question

I want to make my own NES cartridge, but I don't know what the correct type of ROM chip would be.

I am specifically thinking about the simplest PCB that works, an NES-NROM-128 which consists of a 16 KiB PRG, and an 8 KiB CHR ROM, like Baseball:

I assume these are some kind of standard ROM Chip, so I wonder if there are current off-the-shelf chips (preferably EEPROMs so that programming is easy - by which I mean that pulling out the chip and putting it into a programmer is fine, but no UV windows or one-time burn process please) that I can just buy brand new.

And if yes, are they part of a standardized family, so that I could e.g., get a 32 KiB one if I want to make an NES-NROM-256, or a larger one if I find or make a mapper chip?

There's a bunch of EEPROMs on the market, but I'm thinking about stuff like voltage levels, compatible pinout to go directly to the edge connector without a mapper/glue chip, and speed/access times/latency (if that matters - I know if does with some SRAM chips, but no idea about ROM)

(I am ignoring the issue of the 10NES/CIC here, and I am not looking at solutions like Flash Carts - I want to make a "real" NES or Famicom cartridge. I also don't want to reprogram an existing ROM of a donor cart)

Answer 1

Drop-in replacements

For the simplest option, seeing as the board that you show uses 24 pin ICs, then I would suggest the following EPROMs, as drop-in replacements:

• 27C64 (8 kB)
• 27C128 (16 kB)

or the equivalent sized EEPROM:

• 28C64 (8kB)

Unfortunately, a 28C128 (16kB) EEPROM doesn't seem to exist, even though pin 26 could have been used for A13.

Obviously, the two pins used for programming the 8 and 16 kB EPROM/EEPROM (pins 1 and 27) should be left unconnected and tied high, respectively.

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Larger capacities

You could use even greater capacity EPROMs, still using the same DIP-28 package (with a minor adaptation of the board):

• 27C256 (32 kB)
• 27C512 (64 kB)

Larger sized EEPROMs have 32 pins, due to the additional pins required for programming/addressing, so other PCB designs would be required:

• 28256 (32kB)
• 28512 (64kB)