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).
Thanks
Andrea