"sokolov@alpha.CES.CWRU.Edu" "Michael Sokolov"

>   Bruce Lane <kyrrin2@wizards.net> wrote to me instead of port-vax:
>> ?!!? A -SCSI- RRD40? Pardon my skepticism, but I've only seen them in the
>> proprietary DEC interface with the 15-pin connector. You're sure about
>> that?
>   Absolutely sure. It's an external box with 2 SCSI-1 connectors and SCSI
>ID switches on the back, and I have seen several manuals for SCSI-only
>machines detailing how to attach an RRD40 to the SCSI bus ("Take one end of
>the cable and insert it here, take the other end and insert it there...").
>Seriously, though, I'm quite confused by all these RRDs. This one is in an

The RRD40 came in two variants: one with what I presume is the native interface 
that is driven through a KRQ50, and one with a SCSI interface. AFAIK, the SCSI 
variant was just the same drive but with an additional circuit board to provide 
the SCSI interface.

(The RRD40's proprietary interface was, I think, the same as the RRD50, DECs 
first CD-ROM drive. Both the RRD40 and RRD50 are very slow: a dual speed RRD42 
is a big improvement!).

>   In general the situation will all these RRDs is rather strange. The
>strangest thing is the way in which DEC has assigned model numbers to them.
[snip]

Model numbers rarely make any sense. Usually there will be some kind of order or 
logic to the first few members of a family, but it soon breaks down. So for
example, the DSSI drives are RF3x for the smaller form factor and RF7x for
the larger size, SCSI drives are RZ5x for FH 5.25" and RZ2x for 3.5" HH (but
RZ3x crept in and now the 9GB drive starts a new pattern). And usually the 
bigger number indicates "better" in someway. But DEC's first CD-ROM drive
(a single-speed, non-SCSI tabletop device) was the RRD50, the second one (and 
the first to have an optional SCSI interface) was the RRD40 and the later ones
have simply increased the model number (RRD42 to RRD46).

I wouldn't expect to read *too* much into model numbers.

Antonio

Antonio Carlini                            Mail: carlini@marvin.enet.dec.com
DECnet-Plus for OpenVMS Engineering
Digital Equipment Corporation              Worton Grange, Reading, England