help needed: problem with UNIBUS access on my PDP-11/70

From: Johnny Billquist <bqt_at_update.uu.se>
Date: Tue Jul 16 04:37:01 2002

On Tue, 16 Jul 2002, Gooijen H wrote:

> Going back through my notes I see that the swap RX11 -> RX211
> was the last action. So, back to the previous state: RX211 out,
> RX11 in. Guess what. The hung condition is back.
> The RX11 is a programmed I/O device. I knew that. But thanks
> to Tony's e-mail that older cards *do not* wire CA1 to CB1 if
> they do not use DMA, I checked the RX11. CA1 is not connected
> to CB1. That explains the hung.

And what was the first thing most people said? Check your NPR line!
Perhaps we didn't stress it enough. :-)
But I saw that you had the funny assumption that if a card was inserted
you did't need the check the NPR line. Oh well, you learn something every
day. :-)

Anyway, I'm glad you got it working.

> By experiment I will check the NPR wire of the other UNIBUS slots.
> You know why once you have seen the backplane of an 11/70.

Huh? It's no more difficult checking the NPR wire in the 11/70, than on
any other Unibus backplane. And it *is* rather simple to see if the jumper
is there or not. And it's much faster than doing empirical tests. Just
take a peek at the backplane, and you'll see it.

> G7273 double grant in slot 41 --> THE HUNG IS BACK! Huh??

A bad G7273? Inserted wrong? Something like that anyway.

> Also learned what that "SWR" column means in the M9312 manual.

SWitch Register, yes. :-)

        Johnny

Johnny Billquist || "I'm on a bus
                                  || on a psychedelic trip
email: bqt_at_update.uu.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
Received on Tue Jul 16 2002 - 04:37:01 BST