QBus termination?

From: Patrick Finnegan <pat_at_computer-refuge.org>
Date: Mon Feb 7 19:32:38 2005

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

> 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).

Purdue University ITAP/RCS        --- http://www.itap.purdue.edu/rcs/
The Computer Refuge               --- http://computer-refuge.org
Received on Mon Feb 07 2005 - 19:32:38 GMT

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