Question about UNIBUS terminators, M9300

william degnan billdegnan at
Thu May 26 09:12:16 CDT 2016

On Thu, May 26, 2016 at 9:38 AM, Noel Chiappa <jnc at>

>     > From: William Degnan
>     > Here is the layout starting from slot 9/11 of the expansion cabinet
> Just slot numbers by themselves aren't much use, because if there are any
> non-UNIBUS backplanes (e.g. custom backplanes for core memory, for an RH11
> -
> which has its own custom backplane, you can't use a regular SPC/MUD
> backplane to hold it), we need to know what those are, and where.
> Note that many boards can only go in a specific slot in a custom backplane,
> and vice verse - some slots in such backplanes will only hold a specific
> kind
> of card.
> Taking the RH11-AB as an example: it comes with a 9-slot custom backplane.
> Hex
> RH11 boards M7294 and M7295 go in slots 3 and 2, respectively (and nowhere
> else, and nothing else can go in those slots). UNIBUS A in is in slot 1,
> connectors A/B; UNIBUS A out is in slot 9, connectors A/B. UNIBUS B in is
> in
> slot 8, connectors A/B; UNIBUS A out is in slot 7, connectors A/B.
> <snip>

> It looks like slot 31 starts another backplane. Given the cards that are
> plugged in (LP11, DL11, etc), it's probably a 'UNIBUS' backplane (i.e. SPC
> or
> MUD slots).
>         Noel

Thank you for taking a few to send this information.   I was just curious
about the role of the 9300, to explain the configuration I am working
with.  I am working to get up to speed on UNIBUS architecture.

For now, I am going to focus on getting any DL11-x serial card or two
running...and maybe a configure one to read diagnostics from the teletype
the other for VT220 @ 2400/9600.

AS I had mentioned earlier I had this system running PDPGUI but my
previously-working DL11-W pooped out.  I have the manual, need to diagnose
fix or replace.  I am also working on DL11-x (M7800-x) cards on hand.


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