Early CD-ROM drives (was Re: Free stuff)

From: Eric Smith <eric_at_brouhaha.com>
Date: Sat Jan 25 19:48:01 2003

Tony Duell wrote:
> My only CD-ROM drive is an external Philips unit which is clearly a
> modified CD player. Officially modified -- as in a production run -- not
> some hacker kludging the interfaces on, though. It _looks_ like a CD
> player (and is about the same size), but has a DA15 connector on the
> back as well as a couple of RCA phono sockets for audio out. Inside,
> many of the chips are similar to those in a CD player -- there's one
> extra chip to grab the right part of the data stream and send it to the
> PC, and there's modified firmware in at least one of the
> microcontrollers so that it can take commands from the PC over a custom
> serial interface. The ISA card that links to this has a large ASIC (PLCC
> package), an SRAM chip and a couple of buffers.
>
> I do have the service manual for it, but it doesn't give any details of
> talking to it directly or what's inside the ASICs. Just schematics and
> alignment data for the drive unit itself.

Your descriptions sound somewhat, but not exactly, like the Philips CM100
CD-ROM drive and its associated interface card.

The CM100 is a top-loading drive, but it does not have any audio outputs.
It does not contain any ASICs, though it does use the Signetics CD-Audio
chip set. To that, it adds a *lot* of TTL and CMOS SSI and MSI chips
to reformat the data. The interface to the PC is via four RS422
differential pairs through the DA15 connector.

The microprocessor in the drive is an 8051. I've disassembled the code
into a source file and commented large portions of it.

The interface could have, with only minor changes, supported multiple
drives attached to one controller, but they didn't implement that. They
did put a DIP switch on the drive to select a unit number, but they
didn't put in enables for the RS-422 drivers.

The drive is designed to display some diagnostic information to an
external four digit LED display module made by III-V Semiconductor, a
spinoff of National Semiconductor now known as Three-Five Systems.
These LED modules are no longer readily available, so I programmed
a PIC with a character LCD module to replace it.

Philips also made the CM110, which was a CM100 with an internal SCSI
bridge board added. I haven't been able to find one.

DEC OEM'd the CM100 as the RRD50, and made their own Qbus and Unibus
host adapters for it. I've been looking for those, too.

> I also have the manaul for the CD player that it was based on.

What model was it?

Eric
Received on Sat Jan 25 2003 - 19:48:01 GMT