PDP-11/23 Debugging

Ben Sinclair bensinc at gmail.com
Mon Nov 17 15:12:07 CST 2014

That all makes sense now! I should be running as you described since I
removed the W4 jumper.

I mis-typed on the list of boards... I always have the BDV11 in!

On Mon, Nov 17, 2014 at 2:55 PM, Noel Chiappa <jnc at mercury.lcs.mit.edu>

>     > From: Ben Sinclair
>     > If I setup the BDV11 to control the LTC interrupt, should I have W4
> in
>     > or out?
> If you have W4 in, you can do whatever you want on the BDV11, with the
> front
> panel LTC ('Aux') switch, etc, and it won't make a difference - the machine
> will not do LTC interrupts, no way, no how! :-)
> If W4 is out, _and_ the LTC switch on the front panel is on, _and_ the
> BDV11
> is set up to control the LTC, then the machine will boot with the LTC off,
> and the LTC can be turned on by the software (by storing a '0100' in
> 177546).
>     > I'm currently only running with the CPU, memory, and serial boards
>     > installed.
> Oh, one other thing to pay attention to: not all DEC backplanes have
> termination QBUS pull-up resistors. The H9270 and H9373 (normal equippage
> in
> the BA-11M and BA-11N boxes, respectively), for instance, do not. Those
> machines need something at the end of the bus to provide the
> termination/pull-up - such as a BDV11 or an REV11.
> And then we get to 18 and 22 bit busses... :-)
>         Noel

Ben Sinclair
ben at bensinclair.com

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