PDP-11/23 Debugging

Noel Chiappa jnc at mercury.lcs.mit.edu
Mon Nov 17 14:55:49 CST 2014

    > 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... :-)


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