[TUHS] SVR4 vs. Solaris 2

[Rob Gingell via TUHS]

On 11/11/25 6:04 PM, segaloco via TUHS wrote:
> I often see it suggested that the first version of Solaris was
> SVR4 itself, but my question is: Was the initial stock Solaris 2
> release identical to USL SVR4, ...
No, Solaris 2 was never just SVR4. Solaris 2/SunOS 5.x was built from 
SVR4 but included things that were part of the SunOS/Solaris product 
evolution outside of SVR4. One example would be SunOS 4.x binary 
compatibility.

Like a lot of vendors the product Sun shipped its customers was never 
just the base technology Sun licensed from BSD or AT&T.

On 11/11/25 6:04 PM, segaloco via TUHS wrote:
> ...System V Release 4 was a
> joint effort between USL and Sun, which involved contributions
> from both parties as well as other improvements.
Yes, a joint effort that from the Sun perspective was "in addition to" 
the product we were creating for our customers. Not unrelated of course 
but done in parallel with getting SunOS 4.0 and then 4.1 out, shipping 
new hardware, and supporting a rapidly growing installed base 
contemporaneously.

At the risk of being redundant with previous postings, for background, 
the "joint efforts" between Sun and AT&T had 3 phases:

Phase 1: Sun produces a product that "can be" SVID-compliant. That was 
SunOS 4.1.

Phase 2: produce SVR4. Incorporate 4.2 BSD and the major Sun 
technologies (memory management, dynamic linking, NFS) through SunOS 
4.0. Sun expected to ship SunOS 5.0 based on SVR4.

Phase 3: future stuff. Overtaken by events and abandoned. The Spring 
Research OS in SunLabs came out it.

The marketing transition to Solaris occurred after all this was in 
motion out of rationales that weren't related to the joint work.

On 11/11/25 6:35 PM, Clem Cole via TUHS wrote:
> Remember Sparc was not a
> reference platform for SVR4 (386/486 were). 

True. But, for context, a leading point of the announced plan between 
AT&T and Sun was that AT&T's Data Systems Group planned to ship a 
platform consisting of "Unified System V" and SPARC processors. And 
while of less interest to this audience, that plan, and less so the 
software work that enabled it as discussed here, was the big deal as 
viewed by the executives.

Also, the ABI's were introduced with SVR4 and SPARC was one of those 
(along with x86 and 3B's), and was partly in service to the notion of 
"platforms" as accompanied the announcement.

That platform idea was, for AT&T, another thing overtaken by events but 
it was a key factor in bringing the joint efforts together.

> The big thing Solaris lost was
> the work SunOS had done in the memory system. 

No, that and dynamic linking were taken from SunOS and included in SVR4. 
No loss at all and they were arguably improved in the process, for 
example the transition to ELF cleaned up some contortions 4.x had 
incurred by choosing not to change the object file format in 4.x.

USL managed a pretty difficult SVR4 project in working jointly with Sun, 
and the other licensees, to juggle all our competing demands and 
constraints. That they did that while also overriding their own just 
released technologies like SVR3 shared libraries, and then improving the 
net result by introducing new technologies, like ELF, was pretty 
impressive and generally under-appreciated.