PDP-11/05-NC with M9301?

Guy Sotomayor ggs at shiresoft.com
Thu Mar 17 11:37:29 CDT 2016

> On Mar 17, 2016, at 9:35 AM, Mattis Lind <mattislind at gmail.com> wrote:
> 2016-03-17 17:27 GMT+01:00 Guy Sotomayor <ggs at shiresoft.com>:
>>> On Mar 17, 2016, at 6:01 AM, Mattis Lind <mattislind at gmail.com> wrote:
>>> If one read notes in the PDP-11/04 printset it says: Do not insert a M930
>>> or M9302 in a MUD slot. Only in the Unibus slots or you will have short
>>> circuit. On the other hand it does not say that the M9301 (or M9312)
>> cannot
>>> be installed in a unibus slot. It recommends that those boards go into
>> MUD
>>> slots. But electrically I cannot see that it shouldn't work. Especially
>> if
>>> you jumper W1 - W5.
>> Hopefully this will clarify a few things:
>> “Unibus”: These are the AB connectors in the *last* position of a
>> backplane.
>> It allows for bridging between backplanes.  The only “card” that can go
>> these
>> “slots” is a terminator (ie M930) or a terminator bootstrap (ie M9312).
>> SPC: These are the CDEF connectors in any of the slots of a “unibus”
>> backplane.
>> Not all backplanes support SPC slots.
>> MUD: These are the AB connectors in some newer backplanes (usually
>> associated with
>> the extra slots in a CPU backplane…11/34 and 11/04 CPUs have MUD slots).
>> MUD
>> stands for “Modified Unibus Device”.  They are *not* compatible with
>> Unibus slots
>> as they have different voltages present than what are on the Unibus
>> slots.  You *will*
>> “blow out” a board by plugging something designed for a Unibus slot into a
>> MUD
>> slot.
> Yes. That is pretty clear from pin assignment list that bad things WILL
> happen if you try to install a Unibus-slot-compatible device into  a MUD
> slut. But the vice-versa? Installing a MUD-compatible device into a
> Unibus-slot?

Most of those are memory boards and from my recollection they just won’t

TTFN - Guy

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