An unassuming chip, labeled VTI 73192 E4002, lurks within the Atari compatibility products of the 1980s that made Coleco and other video game consoles compatible with the Atari 2600. Here’s what that chip does and why it was important.

What the VTI 73192 E4002 does

VTI 73192 E4002

The VTI 73192 E4002 was a pretty blatant copy of Atari’s proprietary TIA chip.

Other consoles of the day were built from off the shelf parts. The Atari 2600 was mostly off the shelf parts. It had a 6507 CPU and a 6532 RIOT chip providing memory and I/O. Both are standard off the shelf parts that several companies could supply in the 1980s. Nothing about those two chips was exclusive to Atari.

The only chip that was a problem for anyone wanting to clone Atari was the TIA. The Television Interface Adapter. Atari’s part numbers for the chip were CO10444 and CO11903.

The TIA was Jay Miner’s audio/video chip, and it’s the heart and soul of the Atari 2600. Anything wanting to be compatible with the Atari 2600 needed that chip, or a perfect copy, to function properly. Otherwise it would glitch or crash on all but the simplest games.

The TIA was Atari property. It dated to 1977, so its patents wouldn’t expire until 1994.

Some people have speculated that so many companies made the TIA for Atari that it was a de facto off the shelf part. That is incorrect. It was still Atari’s design, so anyone seeking to sell it to someone other than Atari needed Atari’s permission.

Coleco sourced a clone from another company, VTI, later known as VLSI Technology Inc.

How VTI got around Atari’s patents

It’s unclear whether Coleco or VTI did the actual design work, but VTI also sold the same chip to Mattel for their 2600 compatibility module for the Intellivision console. The TIA clone accounted for 69% of VTI’s revenue in 1982, according to the trade publication Electronic Business Today.

This chip was the basis of the Coleco Gemini game console, the Coleco Expansion Module #1 for the Coleco Vision that added 2600 compatibility, and Mattel System Changer. No doubt Cardco would have used it in the Cardapter 1 compatibility module for the Commodore VIC-20 as well.

By the accounts I can find, VTI’s clone was more of an outright copy. The design basically sliced Atari’s design into four pieces and moved them around. It wasn’t a true clean-room reimplementation, the way Compaq cloned IBM’s PC. As such, it presented considerable risk of legal problems. If a lawyer could convince a judge that slicing a chip into four quadrants and moving the quadrants around and calling it your own was the same as simply rearranging the chapters of a book and calling it your own, the game was over.

So the short answer is VTI didn’t do much to get around the patents. They just copied and obfuscated Atari’s design.

The result was better than 99% compatible with the original. A very small number of titles from late in the 2600’s lifespan had issues with the compatibility modules, mostly Tigervision titles. Usually it was a problem with the cartridge not fitting, but a small number reportedly don’t work even after an adapter resolves the fit and finish problem. Likely this is due to timing issues from rerouting connections on the chip die after slicing and rearranging the quadrants.

The lawsuit

Atari sued Coleco for $350 million in December 1982, saying Coleco infringed on two of its patents. Coleco counter-sued for $500 million, claiming antitrust violations.

The two parties settled out of court in March 1983, with Coleco agreeing to pay Atari a licensing fee on the two patents. Atari decided it would be more profitable, or at least less risky, to let Coleco sell the Gemini and the expansion module and collect royalty payments. Coleco was on shaky legal ground, but Atari didn’t need antitrust issues.

What about Mattel?

Atari never sued Mattel. Mattel held that its Intellivision System Changer, the Atari 2600 compatibility module for the Intellivision console, used off the shelf parts. They obscured the design by soldering wafers directly to the board and covering them with epoxy blobs.

This made it harder for Atari to prove where Mattel was getting parts. Atari probably decided going after Mattel would cost more than they could get, given the declining sales of the 2600 console by mid 1983.

Atari could have subpoenaed VTI, but by then, Atari was using VTI to reimplement the TIA in a successor chip. Taking legal action against a business partner would have put the 7800 console in jeopardy.

Modern clones

Modern Atari 2600 clones are less of a problem, since the patents expired in 1994. They may use software emulation, or they may reimplement all three chips as a system on a chip design.

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