It was darkest hour for the video game industry following the holiday shopping season of 1982. The torrent of third party developed titles had flooded the home video game console market to the point of saturation. It incited a price war amongst retailers where new releases were dropped to 85% off MSRP after less than a month on the shelves. Mountains of warehouse inventory went unsold leaving a company like Atari choosing to dump the merchandise into the Chihuahuan desert rather than face the looming tax bill. As a result, the whole home video game industry receded seemingly overnight.

One company single-handedly revived video games to mainstream prominence. That company was Nintendo. They’re ostensibly seen as the “savior” of the video games industry, despite the fact that microcomputer games were still thriving (history tends to be written by the victors). Nevertheless their Nintendo Entertainment System (NES) was an innovative console featuring games with scrolling screens, arcade-like sprites. But the tactic they used to avoid repeating the 1983 collapse was to tightly control their market using the Nintendo Seal of Quality.

From the third party developer perspective, Nintendo’s Seal of Quality represented more than just another logo to throw on the box art. It represented what you could and couldn’t do with your business. Those third party licensing agreements dictated the types of games that could be made, the way the games were manufactured, the schedule on which the games shipped to retail, and even the number of games your company could make. From the customer side of things that seal stood for confidence in the product, and Nintendo would go to great lengths to ensure it did just that.

This is the story of how an Atari subsidiary company cracked the hardware security of the original Nintendo and started putting it into their unofficial cartridges.

“There were some urban legends in the very early days of the Famicom. Nintendo allegedly used some strong arm tactics at the retail level and they forcibly discouraged reverse engineering of the platform.” – Mark Morris, Former Tengen Programmer

Here Comes The Rabbit Chip

The other half of the seal was Nintendo’s security lockout system known as the 10NES program. Essentially the program consisted of a “master” IC inside every NES control deck and the identical “slave” IC inside every game cartridge. Upon inserting an official game cartridge and powering on the console, the LOCK on the master IC sends a reset and initialization signal to the KEY on the slave IC. If the correct response is returned the game cartridge boots the game, but if not the CPU/PPU RESET lines are pulled low with a 1Hz square wave accompanied with a solid color blinking screen on the display. Due to Nintendo’s stringent licensing terms if a company wanted to publish on the NES the 10NES program was the only way in… until Tengen came along.

Tengen, a subsidiary of Atari Games, was initially created to port coin-op arcade games onto home platforms like the NES. Tengen hardware engineers sought to reverse engineer the NES CIC through a chemical peel, but when those efforts failed to generate a complete bypass solution the company decided to become a Nintendo licensee. Upon becoming official, Atari Games lawyers sought out a loophole in order to obtain the code for the 10NES program via the US Copyright Office. By stating that Atari was a defendant in a 10NES program infringement case and therefore was privy to that information, however, no such lawsuit existed at the time of the request.

A shady move to be sure, but combining elements of the newly acquired code with the Tengen engineers’ silicon design the NES’ lockout chip was cracked. They called it the Rabbit chip. This chip meant Tengen were the masters of their own destiny, and allow them to release games like RBI Baseball that featured actual MLB players. However, the people creating the games were not aware the Rabbit chip existed.

“I was completely naive to what was going on…I had no idea, I thought we were going through standard Nintendo.” – Steve Woita, Tengen Programmer

One Small Step For Tengen, One Giant Leap For 3rd Partys

Unsurprisingly Nintendo would retaliate against Tengen releasing unofficial cartridges. In 1990, Nintendo of America sued Tengen for copyright infringement of the 10NES program. Tengen’s defense hinged on the idea that the Rabbit chip needed to function indistinguishably from the 10NES chip in order to prevent Nintendo from barring Tengen from releasing games on any future revision of the NES hardware. Tengen even called into question the validity of the lockout system patent for its obviousness, but it was all to no avail.

No doubt emboldened by Tengen standing up to Nintendo, other third party developers like Camerica, Active Enterprises, and Color Dreams created their own 10NES bypass circuits. These methods typically involved creating a charge pump in an attempt to “stun” the CIC lockout chip. Users of those game cartridges were unknowingly causing damage to their consoles’ less voltage tolerant parts, but the allure of having dozens of games packed into one cartridge like Action 52 would be a novelty too sweet to pass up.

At the time, the Nintendo Entertainment System was in 33% of all American households. With that kind of market penetration, other game systems hardly mattered. So a couple of years after the copyright infringement case, Atari Games would challenge Nintendo’s virtual monopoly on the videogame industry in court. The antitrust case brought against Nintendo would not reach a decision as both parties agreed to an undisclosed settlement, however, it stands to reason that if the case had gone in favor of Atari Games the video game world would look very different than it does today.

Tengen challenging Nintendo at the height of their influence ultimately changed the way third party developers coexist with platform holders. Each side would treat each other more like partners, because the success of a video game platform is forever entwined with the software written for it. The introduction of the Rabbit chip set a precedent that no game console security was beyond scrutiny. Who knows if history had gone a little differently we might have received a few more ports like the unreleased Tengen version of Marble Madness in the video below: