PDP-11/05 microcode dump?

Mattis Lind mattislind at gmail.com
Fri May 6 02:19:15 CDT 2016

Has anyone dumped the microcode of the PDP-11/05?

I am looking into a CPU board pair that are not behaving that well. The
only switch that does anything is the START switch. The rest is doing
nothing. The CPU clock is stopped.

When tracing the microprogram flow it looks very suspicious. Comparing the
same sequence with a better working pair reveal a few differences. All
these can be narrowed down to one single PROM chip.

It doesn't look like it is something else that is wire-ored onto the micor
address bus since the enable signals for all those are inactive. And one
signal is already low so wire-ORing would not change it.

I would need a dump of the chips or at least A04A2 / E102 on the Control
board. There are microcode listings in the manual but they need to be
treated to get into a dump. So if someone already have a dump that would be
highly appreciated.


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