On January 17, you wrote:
> I tried putting the Qbus tape controller in the 8200 UNIBUS and it 
> failed ... Yep it IS incompatible

  Definitely...The physical aspects of Qbus and Unibus are similar,
but that's where the similarity ends...The Unibus is a 7mb/sec bus
with 16- or 18-bit addressing used on many of the older DEC machines.
The VAX folks implemented Unibus on the "newer" (meaning non-VAX-11
series) to maintain compatibility with the huge installed base of
Unibus peripherals.

  The Qbus is a newer, slower (3.3mb/sec) bus with 16-, 18-, or 22-bit
addressing that multiplexes address and data lines.

> Would it be possible to hookup the RA81's to the uVAX ? I could copy 
> the software and then boot up on the 8200....

  This is what I would suggest.  Find a kda50 (Qbus sdi disk
controller) and put it in the MicroVAX.  This is the Qbus counterpart
of the kdb50 (BI-version) which you most likely have in your 8200.
Depending on what kind of disks are currently in your MicroVAX, you
may need to readdress the kda50 from the standard 772150 address to an
alternate address such as 760334.  Just FYI, the Unibus counterpart of
these controllers is called a uda50.

  If you do muck about with the RA drives, be careful to use proper
cabling and don't skip any of the nice sdi distribution panels and
cabinet kits...They matter electrically, it seems, and I got bitten
rather nicely by this just a week or two ago, as people on this list
will well remember. :-)

  For what it's worth...I'm very anxious to see 8000-series support as
well, since 8000-series stuff is pretty nice (IMHO) and it's getting
_really_ cheap.  Will we have much of a problem with the BI bus or the
different processors, I wonder?


                       Good luck,
                       -Dave McGuire
                        mcguire@digex.net