PDP-11/45: KM11 replica and CPU debug III

Received the boards and components for the KM11 replica; stuffed and soldered, and it appears to work! There are some photos below. I can easily single-step microcode, clock states, and bus cycles now, which should really help with the CPU debug.

Swapped DAP for a spare, and this has fixed the stuck PC issue. Memory issues remain, but by choosing a working memory range, I can start to toggle in and attempt to execute very simple programs.

The simplest possible program, unconditional branch to self, seems to execute correctly:

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001000 000777         BR      .-0

A register to register data move test does not however:

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001000 010203         MOV     R2,R3
001002 000776         BR      .-2

Control flow is as expected, but the value that ends up in R3 seems to be negated. Still, pretty good progress! Now that I can step machine states, the next step will be to put the DAP out on an extender card and start tracking down signals with a logic probe.

The HP1662A logic analyzer from eBay has also arrived; should come in handy in investigating the memory issue.