General Question about UNIBUS backplanes

william degnan billdegnan at
Mon May 23 09:46:46 CDT 2016

> I have no idea what "3011-cf" is. Isn't it just a a DD11-C backplane with
> power-wring entering from the back, rather than through small circuit
> boards?
> >
> > M7856 10 F-C (RS232 WITH 19.2 OPTION?)
> > G7273 11 C-D
> > 7891 12 A-F (64k MEMORY)
> > M9312 13 A-B (ROM CARD)
> > 672A 13 D (GRANT CONT.)
> >
> That looks like a reasonable setup provided that jumpers W1- W5 are
> installed on the M9312. You should be able to install the RL11 in slot 11
> when you remove the G7273. Make sure that the wire-wrap between CA1-CB1 is
> cut on slot 11 if you install the RL11 there. Also make sure that CA1-CB1
> wire-wrap jumper is installed in slot 13 (or install G7273 card in 13C-D)
> >
> > I am going to switch to another backplane and start over.  Don't know
> what
> > I am doing yet to be honest.  I have to read the manuals and get better
> > educated to properly get these parts working together correctly.
> >
> But all this still doesn't now explain the problem that you cannot access
> (or send characters to)  the serial port. It could very well be the power
> problem as Noel suggested. If I were you I would try to get back to the
> state where it worked, shortening the Unibus to just include the 4-slot
> back plane and the CPU backplane and also remove the RL11 for now. Then
> install the RL11 in slot 11 when everything is working.
> /Mattis
I removed the core backplanes and returned the DD11-C to the orig config
next to the CPU.  I re-inserted cards as-was.  I am not getting comms from
the M7856.  I may have shorted the card.  So, I will work on that for now.
 "One step back"



More information about the cctalk mailing list