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On Mar 29, 2025, at 10:34, shadoooo via cctalk <cctalk(a)classiccmp.org> 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).
Thanks
Andrea