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

From: Gooijen H <>
Date: Tue Jul 16 02:19:00 2002

OK, the continuing story goes on to its conclusion.

It looks I have been bit by the RX11 experiment.
Some evenings ago I swapped the RX11 for an RX211 card, but I did
not have the time to do some tests after the swap. Wish I did ...
But first some replies to suggestions made.
With the RX211 in slot 41, the DL11 in slot #40 and a M9302
+ I can access the diags at 765000 on the M9312 successful
+ I can access the PROM at 773000 on the M9312
+ access to CPU registers and MMR0-1-2 (777572 /4 /6) are all OK.
+ read/write the DL11 registers also OK!

??? I do not have a problem ???

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.

> It's OK to solder a wire (carefully) between the 'inside'
> end of these fingers to make a DL11 (or whatever) that will
> work in any slot. Some of my cards have been modified in
> this way by the previous owner. I don't do that -- I fit the
> wire-wrap jumper on the back of the backplane as DEC intended

Again, Tony has the same thoughts I had yesterday. I did consider
soldering a wire to the first 2 pins on the component side of the
RX11 card. I did not.
To make sure, I put the RX211 back in: all OK again.
I made a note that slot 41 has the NPR wire on the backplane cut
and that slot 40 has the NPR wired on the backplane.
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.

However ... (I will check this again)
RX11 in slot 41 --> hung and we know why.
RX211 in slot 41 --> all OK and we know why.
G7273 double grant in slot 41 --> THE HUNG IS BACK! Huh??

Although the G7273 card puzzles me, I want to thank everybody for
their contribution to solve this problem. I learned a lot from it.
Also learned what that "SWR" column means in the M9312 manual.
I had it right under my nose Johnny! It is even on my website in the
tree "PDP-11/34A/CPU info/options/bootstrap". On that page all the
ROM tables are listed including links.

kind regards,

- Henk.
Received on Tue Jul 16 2002 - 02:19:00 BST

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