On Saturday, March 9, 1991 at 6:24:53 PM UTC-5, Guy Harris wrote:
> >SunOS 3.0 for the *VAX*?? Did this really exist?
> Yes.
> >Who used it?
> The OS group in Sun, on one machine in Sun, "sunvax", an 11/750. It
> wasn't ever made available as a product; it was mainly just a "proof of
> concept" thing. Nobody ever went past 3.0, as far as I know; when Sun
> got its 4.3BSD tape, they brought 4.3BSD up on "sunvax", to provide a
> "reference" machine with 4.3BSD on it (useful for e.g. testing that the
> 4.1 UUCP works over TCP when talking to 4.3BSD machines), and it mainly
> ran that. I don't even think "sunvax" is around any more....

Pardon the penultimate necro post, but thanks for some clues.
I got here because I'm spending a bit of my time trying to bring up
SUNVAX on SIMH and I decided to search and see if was already done.
There is source code for VAX in SunOS 3.4 so the "never went past 3.0"
statement is questionable. So far all I've done is get a working 4.2BSD
in SIMH and start examining the source code. Next is making a tap
file with SunOS 3.4 and loading it into SIMH.

I checked SunOS 3.4 source code against various BSD source code and
I have not found any 4.3BSD source code in SunOS 3.4.

Things do not appear to be as simple as "there are 4.2BSD or 4.3BSD
version files in SunOS". SunOS 3.4 contains a kern_proc.c with:
/* @(#)kern_proc.c 1.1 86/09/25 SMI; from UCB 4.64 83/05/27 */

Which is the SCCS id prior to 4.2BSD:

$ prs s.kern_proc.c
[...]
D 6.1 83/07/29 06:33:11 sam 91 90 00000/00000/00084
MRs:
COMMENTS:
4.2 distribution

D 4.64 83/05/27 12:46:35 sam 90 89 00001/00989/00083
MRs:
COMMENTS:
merge of bill's code plus lint (plus, of course, cleanup of bill's bugs)

The diffs show that only some header files were munged.

--- kern_proc.c 1986-09-25 09:14:49.000000000 -0400
+++ /tmp/kern_proc.c 2023-05-15 09:47:37.156677124 -0400
@@ -1,4 +1,4 @@
-/* @(#)kern_proc.c 1.1 86/09/25 SMI; from UCB 4.64 83/05/27 */
+/* kern_proc.c 4.64 83/05/27 */
#include "../machine/reg.h"
#include "../machine/pte.h"
@@ -7,19 +7,22 @@
#include "../h/param.h"
#include "../h/systm.h"
#include "../h/map.h"
+#include "../h/dir.h"
#include "../h/user.h"
#include "../h/kernel.h"
#include "../h/proc.h"
#include "../h/buf.h"
-#include "../h/vnode.h"
+#include "../h/inode.h"
#include "../h/seg.h"
#include "../h/acct.h"
#include "../h/wait.h"
#include "../h/vm.h"
#include "../h/text.h"
#include "../h/file.h"
+#include "../h/quota.h"
#include "../h/uio.h"
#include "../h/mbuf.h"
+#include "../h/nami.h"
spgrp(top, npgrp)
register struct proc *top;

Parts of SunOS 3.4 are not even 4.2BSD, they are older.