On 3/29/25 12:33, shadoooo via cctalk wrote:
Hello,
I'm searching information about all existing variants of
DEC Unibus in Dual/Quad/Hex flavors.
I read the "UnibusSpec1979.pdf" on bitsavers, which
reports a "Standard Unibus" pinout in the last pages.
However in several backplanes "Small Peripheral
Controller", "Modified Unibus Device" and "Extended
Unibus" are supported.
Maybe also other unlisted Unibus variants do exist (e.g
VAX 11/730)?
I also found the gunkies.org WIKI very helpful, however it
is still quite difficult to compare the pinout differences
(dummy proof).
Where could I find a specific DEC documentation about the
more recent variants, similar to the 1979 specs, but
referred to SPC, MUD, EUB, ect?
Big doubts:
- why DEC, having defined the dual Standard pinout, had
then to implement the quad SPC backplanes?
- why DEC, having defined quad backplanes, had then to
implement the hex (standard + SPC) or (MUD + SPC) or EUB?
I mean: given that in AB all Unibus signals are present
(from specifications), what is the need for CDEF?
Provided that several signals are duplicated in hex
pinout, the backplane will connect homologue signals
together,
or AB bus will always be separated from CDEF bus?
My aim is to design a reprogrammable digital logic board
which could be employed in any system,
using 18bits address or also 22bits (i.e. for 11/24).
In the "old" days, such as the 1970's, pretty much any
DEC-manufactured peripheral was supplied as a bunch of cards
that plugged into a specific backplane section, generally 9
slots, I think. A couple double-wide slots were for the
Unibus in and out connectors.
Some time later, maybe in the early 80's, there were simpler
controllers that fit on a single card, either quad-wide or
hex-wide.
Sorry for being so vague.
Jon
