QBus termination?

[Vintage Computer Festival]

On Tue, 8 Feb 2005, Pete Turnbull wrote:

> > The M9400-YA does have boot PROMs.  I've got one in this 11/23.  The
> weird
> > thing is that the DSD-440 controller was in this system originally,
> and it
> > has its own boot PROMs.  However, the terminator is in a second bus
> > segment.  Does that make a difference?
>
> I don't know what you mean by a second bus segment.  Does this system
> have two backplanes?  Linked by a cable?  Or are you thinking of left
> and right sides?

Qbus is "segmented", each segment having 4 quad slots.  At least this is
what I've observed.  So the system I'm working with now has two 4-slot
quad bus segments, for a total of 8 quad slots.

> Anyway, you should only have one set of boot ROMs.  I think you can
> disable the bootstrap on an M9400, but offhand I don't know how.  Such

And I didn't notice any straps on the board so I'm not sure how either.  I
guess you're just supposed to use the M9400-YA with DEC controllers that
don't come with boot PROMs, or otherwise use a terminator other than the
M9400-YA.

-- 

Sellam Ismail                                        Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger                http://www.vintage.org

[ Old computing resources for business || Buy/Sell/Trade Vintage Computers   ]
[ and academia at www.VintageTech.com  || at http://marketplace.vintage.org  ]