Bob Shannon wrote: 
  The DSD boxes I used do not emulate DEC drives, and
made the 45 meg hard
 drive
 available as a single device. 
Jerome Fine replies:
As far as I know, the DSD 880/8 and the DSD 880/30 all used
only a Qbus controller.  And they accepted the standard DEC
device drivers in RT-11.
There may have been other DSD boxes in addition the the DSD 880
and DSD 440, but I had not heard about them, let alone the details.
  I have, err, well, Jay West has a DSD floppy-only
(RX-02) emulation in
 his 11/34a out
 in my garage, and that does use the standard driver. 
That was the DSD 440 which emulated the RX02.  For this drive,
I used BOTH a Unibus controller on a PDP-11/34 and a Qbus
controller on an LSI-11 within a VT103.  What I found MOST
amazing at the time (1979) was that the same RX02 floppy would
BOOT on BOTH the Unibus and the Qbus systems even though
the hardware was so different - especially the CPUs.  RT-11
was able to self-configure on the fly to whichever hardware was
present during the boot phase.
  I guess DSD had many varients, and we must be talking
about different
 products. 
Seems like it.  BUT the header stated DSD 880, so I went along
with it.  Any idea what the actual hardware was?
  But the unibus version of the DSD interface for the
floppy-hard drive
 combo's I've
 worked with all needed a DSD driver for RT-11. 
Again, was that a DSD 880/8?  If so, DSD did provide a driver
for the RL02 interface which normally used 10 MBytes to allow
for the 8 MByte hard drive.  I don't feel that this was a special
DSD driver that was essential since the standard DL(X).SYS
could be used with the DSD 880/8 to give a 5 MByte usage
of the hard drive as an RL01 drive.  That meant that 3 MBytes
were lost to the user, but it would still work with the standard
distributed DEC  RT-11 device driver.
Sincerely yours,
Jerome Fine
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