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18 Oct, 25 tweets, 6 min read
in 1990, a tiny company nobody had heard of, Cadtrak, sued Commodore for patent infringement and won. Their company CEO bragged that he put Commodore out of business! Commodore's downfall took more than just that, but who was Cadtrak, and what was their patent? 🧵
first, the patent. 4,197,590, filed in 1978. it described a method for drawing a cursor and then erasing it again without having to store a copy of the background. this was a simple XOR operation.
you see, with an XOR, a '1' bit in the cursor caused whatever graphics were on the screen to get inverted. XOR it again with the same bit, and it gets inverted back to the original state. a '0' bit made no change. this saves RAM, since you don't need to keep a backup image.
but before we dig into the details, let's look into the inventor of the product, Dr. Josef Sukonick. he's a brilliant MIT PhD mathematician.
in 1970 he starting working for a small CAD company called Calma, who at the time made digitizing tablets for computers. when he arrived, he designed and built a minicomputer-based CAD system called GDS (Graphic Design System).
GDS is the granddaddy of all IC layout; in fact, the data format GDSII is still commonly used for transmitting IC mask layout data!
eventually Dr. Sukonick got tired of Calma and left in 1975 to start his own company, Nugraphics. unlike the vector displays that were common at the time, he decided that the future was in raster graphics.
raster graphics require a frame buffer to store the screen image, and they became viable in the 1970s because the price of RAM had fallen, but vector storage tubes were still expensive.
two years later, in 1977, Nugraphics introduced the Cluster 1000, an early raster graphics terminal. they were not a major playor and very little information is available about their products. Cadtrak bought them in 1981.
but Cadtrak was doing poorly. in the early 1980s they had an idea: shut down the production line and switch to licensing patents! they trimmed their staff back to just six people. nowadays we'd call this a pivot.
their business was no longer building physical hardware or software, but litigation and licensing! Dr. Sukonick lost interest in this business and left Cadtrack in 1985 to join Valid Logic (now owned by EDA juggernaut Cadence)
anyway most companies found it easiest to avoid a million-dollar lawsuit by paying Cadtrak a licensing fee. this was typically 2% of revenue!…
i suspect this number was carefully chosen--if it was too high the company might go to court anyway. this strategy was successful. Cadtrak received royalties from 400 companies, including Everex and Western Digital.
certain key companies could have challenged Cadtrak in court and likely would have been able to invalidate the patent. there's definitely prior art. for example, let's take a look at the Xerox Alto.
the clever engineers at Xerox invented the BitBlt function which can copy 2D images around a framebuffer. instead of just copying, they allowed several different operations to be performed, including XOR!
of course, to figure out who came up with the idea first, you'd have to challenge the patent in court, and nobody bothered to do it because of the associated legal costs.
Cadtrak was not the first to abuse the patent system. probably the most (in)famous was Jerome Lemelson. he liked to be known as a prolific inventor, but he never actually built most of his inventions. i'd say he was a prolific patenteer.
Lemelson used a technique known as a patent submarine. the loophole has since been closed, but the idea is to file a patent, and then to use procedural means to delay its issuance until multiple companies are using it unknowingly, and then "surface" it and file lawsuits!
using this simple trick and others Lemelson collected >$1.3 billion in royalties! he also founded the Lemelson Foundation--whenever i hear them announced as a sponsor on NPR, i think of submarines.
but he wasn't all bad, apparently he advocated for a "first to invent" process which i agree with, at least for establishing priority.
why "first to invent"? a "first to file" system can be abused: say you find something that has been invented already but not disclosed to the public. if you patent it (even though you didn't invent it), you can now sue the *actual* inventor and win because you filed first!
in the Cadtrak example, a first-to-file system would have given them priority despite competitors demonstrating non-public (trade secret) prior art*
the US was the last country with a first-to-invent system, but then it switched over to first-to-file in 2013. the worldwide system now favors large corporations at the expense of individual inventors. ☹️
*disclaimers: i am not a lawyer. i don't understand the nuances of patent law, prior art, IP law, and all that stuff. take everything i just said with a grain of salt. have a nice day!
a bit of clarification on first-to-file vs first-to-invent.

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