[TUHS] Did System V Really Prevent 5BSD?

[Luther Johnson via TUHS]

If you look at the dates on the files in the TUHS Unix tree, pdp11v 
(System V r1 for PDP-11) files are dated 10/11/1983, so I've always 
thought that System V release 1 must have been then. For example:

https://www.tuhs.org/cgi-bin/utree.pl?file=pdp11v/usr/src/cmd

On 12/28/2025 06:12 PM, Clem Cole via TUHS wrote:
> 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.
>>>>