strange number corruption on pdp11/34

Noel Chiappa jnc at
Tue Jan 27 14:24:01 CST 2015

    > From: Jacob Ritorto

    > I'm getting all zeroes nearly any time there's supposed to be a large
    > number output to my terminal.

It sounds like the CPU may be too broken to run diagnostics. Why don't you
try writing some small programs to test various bits and pieces of the CPU
(e.g. add instructions, etc), and toggle them in, and try and find what's
busted that way? (Although for 'add', if the thing's that broken, I'm amazed
it even boots.)

Here's an example:

It's probably too long to toggle in, but you could steal pieces from it
and try them.

I'd probably try out the shift and multiply instruction to start with; trying
to figure out what's probably not used during booting, but could be used
during number printing, those are two good bets.

Anyway, there's no point to running diagnostics until you get that first
problem fixed.


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