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

From: Pete Turnbull <>
Date: Mon Jul 15 16:43:01 2002

On Jul 15, 10:14, Gooijen H wrote:

> - The "golden" tip from Tony. Removed the M9302.
> No more hung! XBUF status shows octal 200 (indicating TX buffer
> empty, ready to receive byte to transmit). Store octal 71 in the
> TX buffer and a "9" appears on the VT320!!
> Basically, I have a complete working machine, but ...
> - Put an M930 as terminator in the 11/70. Still all is fine.
> - Put an onther M9302 (from the working 11/34C) in the 11/70.
> The hung is back.

I got caught by that exact same thing a few months ago, and once again it
was Tony who reminded me of what I once knew: the 9302 makes it hang if the
grant chain is broken. I was tidying up an 11/34 which I was trading to a
friend, moved some boards, forgot an NPR jumper, and spent two days trying
to figure out why the RUN light came on and I couldn't HALT the CPU.

Pete						Peter Turnbull
						Network Manager
						University of York
Received on Mon Jul 15 2002 - 16:43:01 BST

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