Pinouts for the P4 connector in 3/80, maybe others?

[Romain Dolbeau <romain%dolbeau.org@localhost>]

TL;DR: looking for pinouts of the P4 connector in 3/80, possibly other
sun3x (3400 CPU board) and early sun 4 (4300 CPU board)

I don't remember ever seeing this one documented anywhere, but maybe
someone here knows!

I'm looking for the pinouts of the P4 connector in the 3/80, which is
documented as different from the one in the 3/60 and 4/ systems.
Physically it's easy, it's a 3x32 pins DIN 41612 connector, extremely common.

And also, how does (if it does) the system detect the framebuffer on
said P4 device (SBus is easy with OpenBoot/OPenFirmware, not sure what
the 3/80 does, haven't tried booting mine n 20 years and the PSU seems
long dead, idly wondering how to resurrect it with a modern display).

I discovered that the schematics for the 3/60 and 3/160 are on bitsavers [1].
The 3/160 one documents the DIN connector on page 28, and those are a
match for the VME specifications, no surprise there. User signals are
used to carry what Sun called the "P2 bus". The data for the "P2 bus",
along with a lot of power, are on the extra third connector.
The 3/60 also documents 3 DIN connectors on page 14, but they are
clearly not the same. P3 seems a match to the 3/160 P3, minus the "P2
bus" signals. That's the right-angled connector to the power supply in
the case, VME-like.
The other two are labelled P1 and P2 and carry a 68k bus (or so it
appears to me) but are not VME; the PDF on bitsavers has a barely
legible correction to 'P2' that seems like 'P4!' to me.
P1 and P2 have identical pinouts. From the picture of a 3/60
motherboard, they are likely P4A and the (unsoldered in pictures) P4B
connector. P4A is clearly the P4 for the optional color framebuffer.
So that one is actually "documented" :-) But I don't have a 3/60...

Unfortunately, it seems no schematics of the 3/80 ever surfaced. The
P4 is likely very similar for the '030 instead of the '020, so might
carry /STERM, /CBREQ, etc. But without the pinouts, not much that can
be done. The multilayer board is very dense and I can't trace it
properly (at least not non-destructively).

An interesting thing is the documentation for the cg8 framebuffer in
the FEH [2].
There are 3 different P/N including one for the 3/80 backplane, but
otherwise aren't mentioned as different except for the 3/80 variant
using a little bit less power.
A footnote even mentions that "CG8 must be 501-1374-04 or greater for
use with Sun 3400 and Sun 4300 CPU boards".
None of the P/N are 501-1374, BNC is closest (501-1374).
It suggests the 3/ and 4/ CPU board shares the same P4 ? And that they
could be close, or even identical except for the backplane, to the one
in the 3/80.

So I'll extend my question - does anyone have documentation on the P4
as used in any of the P4-supporting systems other than the 3/60 ?
(i.e. 3/80, 3400 or 4300 CPU board).

(I'm thinking about a version of the SBusFPGA [3] but for the '030 bus,
including some Macintoshes' PDS slot, and the P4 seems to fit the bill).

Thanks & cordially,

Romain

[1] <http://www.bitsavers.org/pdf/sun/sun3/3-60/Sun-3_60_Schematic_Jul87.pdf>,
<http://www.bitsavers.org/pdf/sun/sun3/3-100/Sun-3_160_Schematic_Jun88.pdf>
[2] <https://shrubbery.net/~heas/sun-feh-2_1/Systems/Sun4/GRAPH_CG8_Clr_Frm_Bffr.html>
and <https://shrubbery.net/~heas/sun-feh-2_1/Systems/Sun3/BOARDS_18_Video-P4Bus.html>
for all P4 options for Sun3,
and https://shrubbery.net/~heas/sun-feh-2_1/Systems/Sun4/BOARD_Video_P4_Bus.html>
for all P4 options for Sun4
[3] <https://github.com/rdolbeau/SBusFPGA>

-- 
Romain