QBus termination?

[Patrick Finnegan]

Doc Shipley declared on Monday 07 February 2005 06:37 pm:
> Patrick Finnegan wrote:
> > On Monday 07 February 2005 18:18, Vintage Computer Festival wrote:
> >>So what's the definitive requirement for terminating QBus?  I get
> >>various non-answers from various people and it's quite annoying.
> >>
> >>How does one properly terminate Qbus?
> >
> > The CPU terminates one end, and no terminator is required at the far
> > end, unless you connect chassis together.  No machine I've ever seen
> > has had a QBUS terminator in it (other than the termination the CPU
> > provides)
>
>    But some Qbus boards do terminate the bus.  RQDX3 does, and I'm
> fairly certain the RQZX1 does as well.

The RQDX3 doesn't, but an RQDX[1] does.  Also, a BDV11 and an M9400 do as 
well.

>    I also have a Qbus terminator board.  No bootROMs or diags, just
> the terminator.

I've got one of those (M9400) from my 11/03 that's in my 11/780, so I 
guess I discounted that.  None of the machines I've had have *required* 
termination in order to work, however.

It's certainly not like the termination requirement in UNIBUS systems, in 
that the system will generally work without a terminator at the far end 
(except for systems with "a lot" of cards).

Pat
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