PDP-11/23 Debugging

Holm Tiffe holm at freibergnet.de
Tue Nov 18 01:07:06 CST 2014

Glen Slick wrote:

> On Sun, Nov 16, 2014 at 7:44 PM, Ben Sinclair <bensinc at gmail.com> wrote:
> > Well, I just discovered something interesting... What exactly does the aux
> > switch on the front panel control? I assumed it was power to the AC plug on
> > the back of the machine, but it must do something else. With aux in the
> > down position, it again boots to XXDP! If I flip it up and restart, it
> > drops back to ODT after trying to boot XXDP from the TU58.
> >
> > From the documentation, I don't see that it does anything other than
> > control that AC plug.
> >
> Take a look at the 11/03-L Front Panel schematic on page 19 of this
> scan of the BA11-S Field Maintenance Print Set:
> http://www.bitsavers.org/pdf/dec/qbus/MP01233_BA11-S_schem_Mar81.pdf
> If jumpers W1 and W2 are installed on the front panel PCB then the
> BEVENT line will be pulled down to ground when the AUX switch is in
> the OFF position and I believe that will disable the CPU from
> receiving LTC interrupts.
> Maybe your system is having issues handling LTC interrupts.
> I have one BA11-S with jumpers W1 and W2 installed on the front panel
> PCB and another one with those two jumpers removed, so check your
> front panel PCB to be sure whether or not they are installed, but it
> sounds like they must be in your case if the position of the AUX
> switch causes a behavior change.
> -Glen

So far as I remember ifrom my own exeperiments this behavior is pretty
much normal.


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