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Contra Proposal

So I recently got a little bit of internet fame when I posted my proposal to my long time girlfriend on Imgur.


A number of people have asked me for some more technical details on how I did it, so I’ll try my best here to describe the process. I do love retro video games but keep in mind when I started this process, I knew little to nothing about the inner workings of a Nintendo, cartridges, HEX, EPROMs and all this other fun stuff. If you notice anything incorrect, let me know. I’ll try to fix it and chalk it up to inexperience in console and cartridge modding.

Apparently there is a whole forum and scene devoted to NES modding, called ‘repros’, short for reproduction carts. Basically they take NES carts and flash ROMs to the chips and then solder them into real cartridges. This enables you to play super rare or never officially released games on actual hardware. Why actual hardware and not emulators? Well there are a bunch of us ‘purists’ who prefer to play games as they were intended to be played; that is, on original hardware, with original controllers and on a CRT monitor. My girlfriend is one of these ‘purists’ and insists on playing retro games on actual hardware with the actual console. I prefer emulators for their simplicity. Go figure.

First off, I needed an excuse to buy some tools. So I went shopping. Usually MCUMALL is my one stop shop for electronics and components so I hit up there first and picked up:

An EPROM Programmer: PRG-056 True-USB PRO GQ-4X Willem Programmer Full Pack

A UV EPROM Eraser: UV Eprom Eraser Erase Ultraviolet Light Erasable Timer

A new soldering station and heat gun: TOOL-021 SMD hot air rework station 5200(110V-120V)

I won’t say these are the best things ever because there are (much!) cheaper options out there for both of these but this is what I got. For what it’s worth, they do work well and I’ve had no issues with any of these items.

Next up is the EPROM chips. Note that EPROMs are different from EEPROMs. EPROMs are erasable programmable read only memory which differ fromEEPROMs, which are electrically erasable programmable read only memory. In short, EPROMs have one ‘E’ in their name and can only be erased by UV light. This is the reason for the little window on the top of the chip. EEPROMs have two E’s in their name and can be erased by methods other than UV light (like electric). Most NES repros I’ve seen are all done using EPROMs — I assume because they are cheaper. Depending on what NES game you are modifying, that will dictate what chips you need. In order to find that out, you need to hit up NES.db which will show what is inside pretty much every NES cart.

As it turns out, inside almost all NES games are two main chips, a CHR chip and PRG chip. I believe the CHR chip has some graphical info and the PRG chip is the actual game (ROM). Anyway, because I chose to modify Contra the PRG chip was 128k (as stated by NES.db). Callan Brown’s site has an EXCELLENT article about repros and is where I got most of my information from. After consulting that page, I chose to go with 27C1001 EPROMs, buying a bunch because I knew I’d mess up along the way.

To put it all into perspective, here is a shots of the workbench setup:


Note the C1001 EPROMs front and center on the bench. The GQ-4X EPROM programer is still wrapped sitting in the middle. Actual Nintendo and CRT TV are on the left of the bench and the research laptop is on the far left sitting atop Grey Goose case boxes.

Again, not knowing much I decided to test my skills on a few carts to get the hang of programing and soldering everything. This led me to ask my friends for spare/broken NES carts they had lying around. One such cart was Castlevania 3, which had graphics that were glitched upon every boot. I burned a new EPROM on the programer and soldered it into the cart using the pinouts here.


That’s it for now, in part 2 of this post I’ll explain how I edited the contra cart and put it all back together. Hang in there, it’ll be up soon.


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