PDP-11/10 repair started

tony duell ard at p850ug1.demon.co.uk
Mon Oct 5 00:26:02 CDT 2015

> You have no memory, and probably no devices to complete the
> Unibus. So, it is quite likely showing the Unibus is in a
> jammed state.  At the least, you need a Unibus terminator,
> and any bus grant cards between the CPU and the terminator
> (you'd have to check the manual to see how the Unibus is wired.)

The specific issue of an open grant chain locking the Unibus is a quirk
of the M9302 terminator (which asserts SACK under such conditions). This
is unlikely to be a problem on an 11/10.

But you do need some kind of termination/pullups on the Unibus. At least
fit the CPU-end terminator (M930 in the right slot near the CPU boards) if 
you haven't done so already.


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