Re: need a bit of early boot help

[Dave McGuire <mcguire%neurotica.com@localhost>]

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.

               -Dave

--
Dave McGuire, AK4HZ
New Kensington, PA