Tech Flashback: Before ATAPI CD-ROMs, were proprietary interfaces

Nowadays with SATA III, anything IDE is already considered old. But early CD-ROM drives didn’t work with the IDE interface. There were CD-ROM drives which worked over SCSI, but that was quite expensive to implement owing to expensive controller cards. (Old pre-IDE hard disks often used the ST-506 interface which shared some over the floppy connector and a secondary cable).

So instead, Panasonic, Mitsumi and Sony had their own proprietary interfaces, many of them were 34-pin just like floppy drives were. Most of these were MPC1 or MPC2 specification compliant 1x or 2x drives and interfaces, hosted on sound cards.

I was very enthralled to come across this particular drive – which uses the old oddball proprietary interface. Unfortunately, I am not able to test it because while I have some sound-cards with proprietary interface support, I don’t have the appropriate IDC cabling, and none of the cards seem to support the Sub I/F. Even if I did, the next trouble would be the drivers, as these custom interfaces do not behave like IDE/ATAPI interfaces, so require the use of special drivers.

This drive is a Sony CDU33A-01. It is a 2x CD-ROM drive, manufactured by Asco in December 1993. Old drives like these won’t be capable of direct CD-DA Audio extraction, multisession discs, or reading CD-RW discs. These came later.

The back of the drive is somewhat oddball too – notice how the audio uses a floppy-disk power berg connector, and how the molex is situated “upside down”.

Well, I couldn’t help but open it up for a quick peek, given that there’s not a single warranty void seal anywhere. The back of the main PCB is festooned with silkscreen printing and test-points, which show you just how repairable and testable these devices are. There are even alignment pots along the edge of the PCB.

Flipping the PCB over, we can see the plethora of Sony branded chips. One of the chips appears to be possibly a flash/ROM chip in a ZIF socket which allows for easy removal and replacement, especially to upgrade the firmware.

I couldn’t take it apart any further without endangering the drive, so I left it at that. Just another antique, hope you enjoyed seeing it!

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2 Responses to Tech Flashback: Before ATAPI CD-ROMs, were proprietary interfaces

  1. Juan Peron says:

    I got one of these. I came with a Mediamagic ISA card, but it’s unnecessary: the SoundBlaster Pro2 II has a the capability con control it too. It requires a driver called SLCD.SYS, which is very common (you can get it on the web). It’s a slow hardware though.

  2. fraz says:

    I’ve got something similar too. Linux has drivers for them. They are very quiet compared to modern drives, and a while ago (when my computer still had ISA slots) I used it for playing CDs. 🙂

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