Shelby Jueden's Open Source ISA Card Brings Philips' Very First CD-ROM Drive Back to Life

Vintage computing enthusiast Shelby Jueden has taken a rather more circuitous route to adding optical storage to a system than is the norm: finding a rare Philips CM-100 external drive and reverse engineering an equally-rare ISA card to produce a working interface.

"This is a Philips CM-100, the first CD-ROM drive ever," Jueden explains by way of introduction to the project. "This took me years to get and then took longer to get working. This drive was originally released in 1985 and used an early version of the LSMI [Laser Magnetic Storage International] protocol to connect. Later versions of LMSI cards, such as the CM-260, are not compatible with earlier drives."

That poses a problem for anyone looking to step back in time and fire up a Philips CM-100: the CM-153 ISA card, which would have been used to drive the CD-ROM is even rarer than the CD-ROM itself, as many ended up in landfill or gold recovery when their owners upgraded PCs and disposed of the old systems. An obvious external drive may have been saved in a garage just-in-case; a nondescript interface card within a desktop is more likely to have been scrapped.

Having found a fellow collector with a working Philips CM-153 card, early enough to speak the same version of the LSMI protocol as the external drive, Jueden set about reverse engineering it with a view to creating a functional clone — allowing those who are also lucky enough to find a Philips CM-100 or similar-vintage CD-ROM drive to take advantage of its capabilities without having to spend the next few years trying to get lucky on the auction sites.

"[The card] uses all off-the-shelf 74-series logic chips and one 8251A UART controller," Jueden explains. "It [is[ therefore be possible to recreate without needing any rare chips or ROM dumps. A more accurate build will put 7121 in a socket as it must be removed to use the card with an internal drive. If you just want to use it with an external drive this can be omitted."

Jueden has published KiCad project files and Gerber production files for the card on GitHub under an unspecified open source license; his video, on the Tech Tangents YouTube channel, goes into more detail on the reverse engineering process.