DEC DW11 information?

Josh Dersch derschjo at
Fri Mar 3 00:26:27 CST 2017

On 2/27/17 10:02 PM, Tony Duell via cctalk wrote:

> On Tue, Feb 28, 2017 at 4:32 AM, Josh Dersch <derschjo at> wrote:
>> Hi all -
>> Anyone have any technical information (manuals, schematics, etc.) for the
>> DEC DW11 UNIBUS->QBus interface?  I'm curious to know what it's capable of
> I am pretty sure I have the printset for it somewhere. I think the
> VS11 prints also
> include it (the VS11 is a VSV11 with said interface to allow it to be
> used on the
> Unibus).
Yeah, the VS11 drawings have the M8217 schematics, so that's useful.  
It'd be nice to find an actual manual, but it's a good start.

>> and what the requirements are, especially on the QBus side of things.  What
>> kind of backplane is required?  I assume it doesn't support 22-bit QBus
>> devices given the age of the interface (and the complexity required to do
>> so), but does it handle 18-bit devices, or only 16?
> >From memory it handles 18 bit addressing (not 22, of course), interrupts and
> NPR (DMA). The Unibus side (quad card) goes in any SPC slot, you have to
> remove the NPG jumper. It links with a pair of 40 way ribbon cables to the
> Qbus board (dual height) which goes in the 'first' slot of a Qbus backplane,
> where the CPU board wound normally go. AFAIK there are no real restrictions
> on the Qbus backplane, I have used one to hang a MINC chassis off a Unibus
> processor.
> I seems to be transparent in operation. You just acccess Qbus devices at their
> normal addresses.
Cool.  I managed to snag an M8217+M9403 so all I need to do is track 
down/build some cabling to tie the two together (any idea what the max 
length of these cables is?).  I'm kind of hoping I can use it to run a 
QBus SCSI controller, amongst other things.  I'll report back my findings...

- Josh

> -tony

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