Tech Tangents got his hands on a first-generation CM100 drive. That wonderful piece of 1985 technology is not much smaller than the IBM PC it was designed to connect to, and it originally came with its own CM153 ISA interface card. But while most eBay sellers recognized the historic value of a pioneering CD-ROM drive, the accompanying PC was typically a dime-a-dozen model and was thrown out with the rare interface card still inside.

Even after searching high and low for over a year, the only information, Tech Tangents could find about the card was a nine year old YouTube video that showed what the thing looked like.

Luckily, the maker of that video was willing to take high-resolution pictures of the card, which allowed Tech Tangents to figure out how it worked. As it turned out, the card was entirely made from standard 7400 series logic chips as well as an 8251 USART, which meant that it should be possible to design a replacement simply by following all the traces on the board. A after a few weeks of reverse-engineering there was a complete schematic and layout ready in KiCAD.

See the video below and more on drivers on Hackaday with files on GitHub.