Subject: Re: VAX 11/780 progress ... just a little
To: Gunther Schadow <>
From: Johnny Billquist <>
List: port-vax
Date: 09/26/2003 00:08:26
On Thu, 25 Sep 2003, Gunther Schadow wrote:

> Johnny Billquist wrote:
> > To make a short answer: the unibus termination is *vital*.
> > If you fail diagnostics with it inserted, it's not because of the
> > termination, but because some problem in your Unibus don't show up
> > otherwise. The termination should be in the last slot, in AB.
> So, I need grants and NPG grants in front of the terminator?


> When I plug the terminator directly behind the UDA50 (which
> happens to be the last card) things are even worse. The reason
> I don't trust that terminator is that two of the 3 small 
> capacitors seem to have been damaged on the edge. So, may be
> it creates noise on the bus? How can I test that the terminator
> works properly? 

Don't know the answer to that one, but the terminator cards are normally
very sturdy, so a safe bet is that it's ok.

> Ahh, but that is not properly installed, right? If I have a 
> 9 slot UNIBUS backplane, then only the last slot (A,B) can
> have the terminator, right? So, I should put in more cards
> and grants in slots 7 and 8, right? Do I need to put a grant
> also in slot 9C (since the terminator is only in 9A and B)?

Yes, yes and yes.


Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email:           ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol