PDP-11/70 debugging advice

Fritz Mueller fritzm at fritzm.org
Fri Feb 5 02:29:11 CST 2021

> On Feb 4, 2021, at 9:45 PM, Josh Dersch <derschjo at gmail.com> wrote:
> The 11/70 is now somewhat operable.  I can examine and deposit memory, at least for a short while -- after the system warms up for 30 seconds or so the Load Address switch stops functioning.


One handy test on '45 is to put the data display knob to bus address; if the microcode is still running in the control panel idle loop (halt switch down or fault) the data lights will follow along with the toggles.  This is a super quick way to tell if the microcode is still running or if it is wedged.

(The '45 and '70 microcode seem quite similar, so your '70 might have the same feature?  I haven't looked at the flow diagrams yet to know for sure.)


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