The Coleco Expansion Module 1 was a product that added Atari 2600 compatibility to the ColecoVision game console. The product immediately allowed Coleco to claim the ColecoVision had the largest software library of any game console. It is a famous but widely misunderstood product.

Not really an emulator

Coleco Expansion Module 1

The Coleco Expansion Module 1 was basically an Atari 2600 that plugged into the front of a ColecoVision console. This gave the ColecoVision access to the large library of Atari 2600 games.

The Coleco Expansion Module 1 was frequently called an emulator, but that was a bit of a misconception. The ColecoVision was not powerful enough to emulate the Atari 2600 in software. Emulating the Atari 2600 in software alone wouldn’t really be practical until the 386 or 486 era, about a decade later.

Instead, the Expansion Module 1 was really more of a full 2600 clone that plugged into the front of the console and just used the host console to provide power and video output. It wasn’t emulation so much as it was bolting two systems together.

The reason for this was because the two systems had no major parts in common. Software emulation was not a new concept at the time. Bill Gates and Paul Allen famously developed their first successful software product by emulating a computer they couldn’t buy on a mini computer they did have access to. But there wasn’t enough power differential between the ColecoVision and the Atari 2600 for the ColecoVision to do the emulation in software.

How the Expansion Module 1 worked

Coleco Expansion Module 1

The chip in the top left got Coleco sued for infringing on Atari patents.

Instead, the Coleco Expansion Module number one was almost an entire Atari 2600 clone implemented on a module that plugged into the host system to draw power and send video output back through. The design is close enough to being a standalone system that Coleco did develop and release a full 2600 clone a year later. It’s hard to say whether Coleco was keeping its options open, making the system easier to develop, or a combination of the two.

The Atari 2600 was a fairly simple design, with three computer chips doing all of the heavy lifting and a few support components. Two of the chips, a 6507 CPU and 6532 RIOT, were standard off the shelf parts. The original designer, MOS technology, produced the 6507 as a cut down version of the more famous 6502 processor to help Atari meet an aggressive price point. It was just a 6502 with fewer address lines, so it couldn’t address a full 64 kilobytes of memory.

The TIA problem

But the heart and soul of the machine was a chip called the TIA, for Television Interface Adapter. It produced the graphics and sound. It was a trip designed by the legendary Jay Miner while he was working at Atari. Atari didn’t have the facility to produce this chip themselves. They had to outsource production, the same way Apple and AMD design chips today but outsource production to other companies.

There has been some speculation over the years that Atari had so many other companies producing that ship that it was a de facto off the shelf part. But that’s not the case. Atari may have had a dozen different suppliers, but their agreement with those suppliers did not mean they could sell the chip to anybody else.

So while Coleco could easily get supplies of a 6507 and 6532, they needed to clone the TIA.

Coleco found a company willing to give it a try. The company was called VTI, short for VLSI Technology Incorporated.

The chip they came up with was almost fully compatible with the original. There are about 19 known titles, mostly from the publisher Tigervision, that give problems. The Starpath Supercharger and its library of 19 titles is also problematic because the Supercharger itself doesn’t fit in the cartridge slot. The fit is part of the reason some of the other cartridges don’t work right. But the Expansion Module 1 was compatible with between 95 and 99 percent of Atari titles, including all of the major hits.

Atari sued. And there have been a lot of misconceptions about that lawsuit.

Legal action

Atari sued Coleco, claiming Coleco had infringed on two of its patents. Coleco counter sued, claiming antitrust violations. And while Coleco did win an injunction that allowed the product to stay on the market temporarily, there is a common misconception that Coleco won the lawsuit. They did not. Instead, the two companies settled out of court, with Coleco agreeing to pay a licensing fee. Two larger and older companies, AT&T and IBM, were facing antitrust action during this time frame, and Atari probably decided they didn’t want any part of that.

Activision successfully sued Atari and won the rights to publish third party software during this same timeframe. A lot of people seem to conflate bits and pieces from the two lawsuits.

Success in the market

The Expansion Module 1 allowed Coleco to claim their console had the largest library of games on the market. And that was true at least until rival Mattel released a nearly identical product for its game console.

If nothing else, it was great marketing. You could play very recognizable versions of popular arcade games native to the ColecoVision. But if you were upgrading from an Atari, you could buy the Expansion Module and play your favorite Atari titles on your new console. It was a better upgrade path from the Atari 2600 than Atari’s own 5200 console in that regard.

It was a good idea, and it spawned some imitators. Mattel created a similar product, but there was also a vaporware product for the Commodore VIC 20 with similar promises.

Decline after initial success

Ultimately the video game crash of 1983 limited the usefulness and appeal of the product. Atari games went from being hot property to sitting in bargain bins over the course of the year, and a number of third party publishers went bankrupt. But perhaps more importantly, Atari decided to become a third party publisher themselves. They had rights to produce a large number of titles from other arcade publishers, as well as their own. So they quickly contracted outside developers to create versions of these titles for other popular consoles.

There wasn’t much reason to buy the Coleco Expansion Module to play Pac-Man and a couple of other Atari titles once Atari released a better version of Pac-Man for the ColecoVision, along with about a dozen other titles. It may or may not have been cheaper to buy the native titles, but it gave a better overall experience.

But even though the product outlived its usefulness sooner than Coleco expected, it did help the ColecoVision gain market acceptance. And Coleco probably could have survived crash if they had executed better on their computer, known as the Adam. But the Adam was late to market, not terribly reliable, and it failed to capitalize on the shift in interest from game consoles to home computers.

So the ColecoVision and the Expansion Module 1 are mostly curiosities today, but they were rather successful during their brief time on the market. In spite of their short lifespan, they aren’t exactly rare.