Dear Gunnar,
   
   Thanks for the VMS licensing info!
   You write:
> My VS3100 M38 has the daughter board, a floppy drive and two SCSI
> busses:
   You have an RX23S. VS3100s could have the 3.5" floppy disk drive (FDD)
in two ways. One could have a SCSI/MFM daughterboard and a standard FDD
connected to the MFM controller. Alternatively, one could have only SCSI
and no MFM, but in this case the FDD is SCSI. I think that DEC has never
put the SCSI/MFM daughterboard in M38, only in M30, but I'm not sure. You
clearly have a SCSI/SCSI daughterboard and a SCSI FDD.
   As it happens, I'm interested in RX23s. I like good old classical
hardware not only in VAXen but also an IBM PCs. I want my home IBM PC AT-
compatible to have real parts, rather than the "modern" junk. For instance,
I'm using two 5.25" full-height ESDI Winchesters with ~600 MB in each
instead of an 1.2 GB IDE 3.5" "hard drive". Similarly, I want my FDDs to be
classical too. First of all, I prefer 5.25" to 3.5". Second, I want to be
able to write 360 KB disks that can be read reliably on a 360 KB drive, so
I have such a drive in addition to the 1.2 MB one. But since on rare
occasions I need to interact with the outside world, I need a 3.5" FDD too.
This means 3 FDDs total, and I had to MAKE a special controller. Each of
three FDDs must be classical. It must have a removable 330 ohm termination
resistor rather than a soldered-in 1 kohm one. It must adhere to the
SA400/SA450 specification, i.e., it must be designed for an Abstract
Generic Computer, rather than for a "modern PC". Among other things, it
must have jumpers to select the unit number and the function of pin 34.
Finally, it's preferable if it has a real TTL interface, rather than a
CMOS-based "TTL-compatible" one. I have already found suitable 1.2 MB and
360 KB drives. For the 1.2 MB drive I'm using a DEC RX33. It's a fully
classical and fully generic FDD. It can be put in both IBM PC ATs and VAXen
by setting the jumpers differently. The only thing that I still haven't
found is a suitable 3.5" FDD. I'm currently thinking that DEC RX23 may be
suitable for my highly demanding taste.
   Gunnar, would you please look at your drive and answer some of my
questions? First, how is it made to be SCSI? Is it native SCSI (does it
have the SCSI connector right on the drive?) or is it a standard
SA400/SA450 FDD with an adapter board sitting between the SCSI bus and the
familiar 34-pin SA400/SA-450 interface? If it's native SCSI, stop here. If
the drive itself is really SA400/SA450, please examine it. What jumpers
does it have? Does it have unit selection jumpers? What about pin 34? Is
the termination resistor removable or soldered in? What resistance? Is the
power connector big (5.25" type) or small (3.5" type)? Is the interface
connector card-edge or header? How old does the drive appear to be? What's
its front bezel color? Is it mounted in a 3.5" bay or in a 5.25" bay? If
the latter, what kind of mounting adapter is used?
   
   Sincerely,
   Michael Sokolov
   Phone: 440-449-0299
   ARPA Internet SMTP mail: sokolov@alpha.ces.cwru.edu