23 Apr
2001
23 Apr
'01
9:34 p.m.
I think the board he is talking about is a SCSI
<==> audio CD
interface...
The board is an LSI-SCSI adapter. This allowed the
drives to be used in a SCSI system. When I used one
of these drives with a MicroVAX 3900 there was an
interface that drove the drive directly. The RRD40
drives are slow, and the adapter makes them slower.
An RRD42 is a much better and easier to use drive.
The original CD (not CD-ROM) interface is a three (or
four) wire
affair with Left/Right, Clock, Serial data which is fed into
a DAC to produce music... The early CD-ROM drives took these
signals, recognized the sector header (00-FF-FF-FF-FF-00 IIRC)
and decoded the data. Presumably, some extra signals were added
to control seeking, etc...
The audio interface wasn't used with the SCSI adapter.
I've got one of these boards, and I suspect the
parts removed
were: 80C31, 27C256, and NCR 5380 (only parts socketted).
The drive is completely useless without these chips.
The drive is certainly useable with these ICs. They just
can't be used in a SCSI system, but then again, with the
slow access and weird, hard-to-handle caddies, that's no
loss.
--
Eric Dittman
dittman(a)dittman.net