I wanted to make a post with more info about adding the EEPROM for anyone else wanting to give this a shot. First, here's a list I found of all the 64 games (I believe) and their save type along with EEPROM size. This can be useful if anyone is looking to buy one of these carts and wants to know what they're getting into. There's a lot of options for cheap 4k EEPROM, for the 16k if you get Conker's it seems like Star Wars Episode I: Racer and Excitebike are your best bets. Next, here's a pinout that I found for the EEPROM from this website: I went ahead and just snapped off pins 2 and 7 since they're NC. Here's what my board looks like: Like I mentioned in my prior post, it seems tempting to use the negative battery terminal connection for ground but it's not actually ground which is why there's a mess of solder and a wire coming off of it and going to an actual ground point. I didn't feel comfortable with trying to scrape at this board to expose traces because it seems to be pretty cheaply made, so I decided to solder to the top of the cart pins. If you're using thin kynar wire you can still get the black dust guard over them. Your connections should be: (written as EEPROM -> cartridge) GND pins 1 & 4 -> GND (I stripped out a small section of the middle of the wire and used a single wire to tie these pins together) CLK pin 3 -> cart pin 19 (1.6MHZ) DATA pin 5 -> cart pin 21(S_DAT) (notice that with this pin there is a point above the pin that the wire can be soldered to) /COLD_RESET pin 6 -> cart pin 20 (/COLD_RESET) VCC pin 8 -> cart pin 17 (VCC) (notice that with this pin there is a point above the pin that the wire can be soldered to) Have fun!