An 8-bit ISA card being plugged into a motherboard

Reverse-Engineering An ISA Card To Revive An Ancient CD-ROM Drive

Being an early adopter is great if you enjoy showing off new gadgets to your friends. But any new technology also brings the risk of ending up at the wrong side of a format war: just ask anyone who committed to HD-DVD fifteen years ago. If, on the other hand, you were among the few who invested in CD-ROM when it was first released in the mid-1980s, you definitely made the right choice when it came to storage media. However, it was a bit of a different story for the interface that hooks up the CD drive to your computer, as [Tech Tangents] found out when he managed to get his hands on a first-generation CM100 drive. (Video, embedded below.)

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.

A 3D rendered image of an 8-bit ISA cardLuckily, 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. [Tech Tangents] set to work, and after a few weeks of reverse-engineering he had a complete schematic and layout ready in KiCAD.

After the PCBs were manufactured and populated with components, it was time to test the new card with the old drive. This wasn’t a simple process either: as anyone who’s tried to get obscure hardware to work in MS-DOS will tell you, it involves countless hours of trying different driver versions and setting poorly documented switches in CONFIG.SYS. Eventually however, the driver loaded correctly and the ancient CD-ROM drive duly transferred the files stored on a Wolfenstein 3D disk.

If you’re lucky enough to own a CM100 or a similar drive from that era, you’ll be happy to know that all design files for the CM153 clone are available on GitHub. This isn’t the first time someone has had to re-create an interface board from pictures alone: we’ve seen a similar project involving a SCSI card for a synthesizer. Thanks for the tip, [hackbyte]!

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Up Close And Personal With An 8x Floppy Controller

In need of a floppy controller for a 286 he was working on, [Gadget Reboot] took to GitHub to see what was available in the open hardware space. There he found an ISA board capable of controlling up to eight drives from [Sergey Kiselev] called the Monster Floppy Disk Controller (FDC) — arguably overkill for the task, but too impressive to pass up. Luckily for us, he decided to document the build process in a video that covers everything from ordering the boards to configuring the BIOS.

Testing with four drives.

The video starts with a high-level overview of the schematic, which as you might have guessed, essentially puts two identical floppy controllers on the same board. You can tell this design was put together during the current chip shortage, as [Sergey] was careful to include some wiggle room if certain parts became unavailable and had to be swapped out for the alternatives listed in the BOM. It’s a decision that already paid off for [Gadget Reboot], as in some cases he had to go with the second-choice ICs.

[Gadget Reboot] was in for something of a surprise when he submitted the board for fabrication, as selecting the option for gold contacts on the edge connector made the production cost jump from $5 to nearly $300. He details how he was able to bring that cost back down a bit, but it still ended up being more than 10 times as expensive as the base price.

The second half of the video is dedicated to configuring the Monster FDC, which will certainly be a helpful resource for anyone looking to put this board to work in their own system. [Gadget Reboot] demonstrates using the board with “only” four floppy drives, and everything looks to work quite well.

Of course if your needs aren’t quite so grandiose, we’ve seen some more expedient floppy controllers which might be closer to what you’re looking for.

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ISASTM Runs Vintage Cards Over USB

The ISA bus is a relic of the distant past, and no longer supported by the PC mainstream. Outside of retro fanatics and likely some long-term industrial users, it’s all but forgotten. That hasn’t stopped [Manawyrm] from hacking away, however, and he’s developed a nifty adapter for the modern era.

Still in its early stages of development, the ISASTM is a ISA-over-USB adapter that allows a modern computer to work with older expansion cards. Running on an STM32H743, and using the microcontroller’s native USB1 interface, the ISASTM card is able to be slotted into a backplane in order to address multiple cards with one adapter. [Manawyrm] demonstrates the hardware by running Monkey Island 1 in the PCem emulator, with sound provided by an AdLib ISA soundcard.

There are some throughput issues, which [Manawyrm] aims to solve by switching to USB2 and making some tweaks and improvements to the code. Regardless, it’s an impressive tool that we imagine could have some use in keeping some legacy hardware alive, too. Incidentally, it’s been a long while since we’ve seen a solid ISA hack around these parts. Video after the break.

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