On 11/11/25 05:52, Johnny Billquist wrote:
And VMS also hangs after printing a banner... Which would suggest
that there is something funny either with the printing on the
console, but which is interrupt related, or something else is
getting the machine stuck at an elevated privilege mode, preventing
interrupts from being processed.
I would actually probably suspect something else isn't completing,
and the processor is stuck at some elevated prio. The console is
probably working just fine, including when interrupt driven. But
something else is not.
I assume we're talking about a real machine here. So it has actual
Unibus. Simple suggestions would be to remove everything not
absolutely required to get the machine running, and really make
sure you have bus grants in all Unibus slots not having a card in
it. Also, make sure the NPR jumper is in place. This one can be a
bit tricky, since it's actually a wire on the back side of the
backplane, which might have been cut. There a double height bus
grant cards that also covers the NPR signal, but the small square
ones do not.
And if the Unibus isn't properly configured, you can probably get
things hung/stuck for some time.
It's a 780, Unibus is not involved here at all :-)
The PDP11 is connected directly to the backplane (SBI).
Well. Yes an no.
The PDP11, which is the FE, don't have any Unibus at all. And the
machine boots, and there is terminal I/O to the console, and the
system starts running.
But something happens somewhere along the way. And the *VAX* have a
Unibus, and it will be probed somewhere along the way, and that is
where I wonder what might be going on.
I don't think there are any problems at all with the PDP11 FE.
[I had sent this last night, but it didn't make it to the list,
presumably due to the attached photo...sending without the photo this
time]
Summary: IT RUNS!
The problem was in the CIB board, a failed 74S74 flip flop in
interrupt handling.
We'll post pics and such soon.
Thanks everyone for the guidance. We'll try booting VMS on it
later tonight, temporarily from the VAX-11/750's system disk. If all
goes well there, we'll set up permanent system disks for it for VMS,
NetBSD, and possibly Ultrix-32.
Incidentally, this is the same '780 that Gunther Schadow had quite
a saga with on this very mailing list, back in 2002. To my knowledge
he never did get it running. We fixed a number of hardware problems
in this machine, so it's no wonder he'd had such a tough time with
it. It was many months of work, off and on, over several years for us
here at LSSM.