General Question about UNIBUS backplanes

william degnan billdegnan at
Tue May 24 08:37:16 CDT 2016

> But the M9312 has bus terminating resistors (unless you actually desoldered
> those!). Then you have three terminators in your system! One in the M891 at
> the CPU, one in the M9312 in slot 3 of last DD11, and then a M930 in slot 4
> of DD11.
> If you want the M9312 you should put it with W1-W5 installed in the slot 4
> where you have the M930. You should not have both a M930 and M9312 (when
> you have the M891).
> /Mattis

After I sent the email to this group, I checked the M9312 and found it was
terminated.  I was told it was not, I should have checked for myself but I
grew suspicious that it should be by default.  Now, the M9312 is in the
last slot, and I removed the M930.  There is nothing except a grant card in
the 3rd slot.

I fixed the core problem I described in my email.  I also am able to store
into core and run "chase the lights",  I have generally speaking a working
16K system.

Thanks again.

Next - Get a serial card running and resume efforts to boot RT11 from an
RL02 drive.


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