[TUHS] Did System V Really Prevent 5BSD?

[Clem Cole via TUHS]

Interesting.  I need to talk to them as that can’t be right. I’ll believe
they might have been a discussion WRT to calling it 5BSD [which would have
made sense from a stand point of being the 5th Berkeley (UNIX) Software
Distribution tape from the Berkeley Industrial Liaisons Office since the
ILO tried to keep track of the different tapes that folks sent out
[originally CAD tools like SPICE, SPLICE, MOTIS long before and of the UNIX
distributions].

ATT would not have had anything to do with it. System III was released Nov
1981 and System V late 1984 - plus Jan 1, 1984 is when Judge Green breaks
allows ATT to be in the computer business so ATT could not have had
anything to say before then.

Calling it 4.1 made sense because it really was a small incremental
difference from 4.0.  Where numbering got weird was years later with the
4.2 release from CSRG.

The point is that ATTs Summit’s next release at that time frame (pre Judge
Green) was Unix 3.0 (which would be renamed System III) while Berkeley was
already at the 4.x level.

And getting back to BSD the key differences between 4.0 and 4.1 are pretty
small and the time between them was short (Oct 1980 and June 1981).  The
primary differences are the #ifdef FASTVAX stuff that Joy did over the
winter after the dust up that the Stanford folks started  in the fall 1980
- Joy had to demonstrate that Unix was just as fast as VMS (which had been
written in assembler). He instrumented a bunch of the kernel and if a
couple places dropped into assembly and got Unix to perform within a very
small epsilon on everything that DARPA cared about.  So the issue became
that ATT nor DEC was supporting Unix. CSRG does not yet exist.

Bob Fabry goes to ARPA with a proposal (and the results from Bill’s work
they winter) that UCB create a team to fill that void (CSRG) - DARPA would
create an advisory team for them and Berkeley would add the features that
DARPA required.   CSRG was not created until the Fall/Winter 81/82.  [For a
historical prospective, Stanford had counter proposed using DEC/VMS and
Australian Wollongong’s Unix for VMS and the Tek/CMU IP/TCP stack for VMS -
two commercial products and the later FOSS.  As we know Fabry’s proposal
was accepted].


On Sun, Dec 28, 2025 at 6:48 PM Warner Losh <imp at bsdimp.com> wrote:

>
>
> On Sun, Dec 28, 2025, 4:34 PM Clem Cole via TUHS <tuhs at tuhs.org> wrote:
>
>> Right idea, wrong release.  4.1BSD was the “fastvax” update from 4.0BSD
>> and
>> really was an increment from the previous release. 4.1 was triggered by
>> the
>> Stanford push to use VMS for performance reasons as the official ARPA
>> supported OS for the VAX. It was CSRG’s naming of 4.2BSD were things got
>> strange.  When you look at functionality the changes from 4.1 to 4.2 were
>> huge [Henry Spencer’s famous line:  “4.2 is just like Unix, only
>> different.”].
>>
>> As for why CSRG chose to call it 4.2 over 5.0BSD is a bit lost to time. I
>> don’t think ATT was in any position to “demand” anything.
>
>
> I'm pretty sure that 4.1 was going to be 5BSD. I've heard this story from
> Kirk several times. He has a listing he labeled 4.5BSD. It was between 4BSD
> and 5BSD when he wrote 4.5 on the spine. Whatcwe know today as 4.1BSD was
> going to be 5BSD. But when it came time to try to do the paperwork, AT&T
> Balked and insisted no 5BSD since it would be confused with the forth
> coming System V. I don't know the nuts and bolts of the back and forth to
> know if this was a really firm request, or if threats were involved.
>
> I've heard this tale from both Kirk and Eric...
>
> Warner
>
> Being at UCB and
>> my memory of the time was that the folks at CSRG chose to stay away from
>> the number 5 because they wanted to be sure their work was clearly
>> distinguished from ATTs — and while the short lived 3.0BSD release was for
>> the Vax, most people by then associated the numbering 2xBSD to be PDP-11
>> and 4xBSD to be Vax.  Only later did CSRG start to add a suffix
>> (Reno/Tahoe) to distinguish other processors as they branched out.  But
>> when 4.2BSD was released, CRSG had a DARPA contract to support UNIX on the
>> VAX [BTW, they did not have the contract for IP/TCP, BBN had that contract
>> and the stories of the issues this caused had been documented/discussed
>> here in the past].
>>
>> Sent from a handheld expect more typos than usual
>>
>>
>> On Sun, Dec 28, 2025 at 6:08 PM segaloco via TUHS <tuhs at tuhs.org> wrote:
>>
>> > So the prevailing narrative I've heard is that 4.1BSD was so-named at
>> > AT&T's demand to avoid confusion with System V.  However, the timeline
>> > leads me to question this.  4.1BSD is given as having been issued first
>> > June 1981.  Of the Bell lineage, my 4.1 manual also gives June 1981 as a
>> > publication date.  5.0 wouldn't release inside AT&T for another year,
>> and
>> > System V manuals give 1983 (i.e. post-divestiture) publication dates
>> > (although they went to print before, many have Bell logos on the cover
>> > still.)
>> >
>> > In any case, if System V as a product didn't exist until sometime 1983,
>> > how did the fear of confusion with this name prevent the naming of 5BSD
>> in
>> > 1981, two years prior?  Was System V as a future trademark already well
>> > accepted as a given in 1981?
>> >
>> > - Matt G.
>> >
>>
>