[Info-vax] OS Ancestry

[Jeffrey H. Coffield]

On 05/13/2021 07:25 AM, Dave Froble wrote:
> On 5/13/2021 9:06 AM, Bill Gunshannon wrote:
>> On 5/13/21 8:52 AM, Arne Vajhøj wrote:
>>> On 5/13/2021 8:21 AM, Bill Gunshannon wrote:
>>>> I have become very curious about the ancestry of VMS.  (I am
>>>> going to look into some others, but for VMS I do have this
>>>> outlet for information!)
>>>>
>>>> Both Primos and Unix came from people recently working on
>>>> Multics.  Primos went in the same direction as Multics while
>>>> Unix appeared to go in a very different direction.
>>>>
>>>> VMS is more similar to Primos than Unix.  I have seen it said
>>>> that RSX-11 was the immediate parent of VMS.  Was that true?
>>>> Given that, what is the ancestry going back even further?
>>>> Where did VMS actually get its start paradigm-wise?
>>>>
>>>> Anybody here have any of this information?
>>>
>>> The story in Wikipedia is:
>>>
>>> https://en.wikipedia.org/wiki/OpenVMS
>>>
>>> <quote>
>>> In April 1975, Digital Equipment Corporation embarked on a hardware
>>> project, code named Star, to design a 32-bit virtual address extension
>>> to its PDP-11 computer line. A companion software project, code named
>>> Starlet, was started in June 1975 to develop a totally new operating
>>> system, based on RSX-11M, for the Star family of processors. These two
>>> projects were tightly integrated from the beginning. Gordon Bell was
>>> the VP lead on the VAX hardware and its architecture. Roger Gourd was
>>> the project lead for the Starlet program, with software engineers Dave
>>> Cutler (who would later lead development of Microsoft's Windows NT),
>>> Dick Hustvedt, and Peter Lipman acting as the technical project
>>> leaders, each having responsibility for a different area of the
>>> operating system. The Star and Starlet projects culminated in the
>>> VAX-11/780 computer and the VAX/VMS operating system. The Starlet name
>>> survived in VMS as a name of several of the main system libraries,
>>> including STARLET.OLB and STARLET.MLB.
>>> </quote>
>>>
>>> https://en.wikipedia.org/wiki/RSX-11
>>>
>>> <quote>
>>> RSX-11 is a discontinued family of multi-user real-time operating
>>> systems for PDP-11 computers created by Digital Equipment Corporation.
>>> In widespread use through the late 1970s and early 1980s, RSX-11 was
>>> influential in the development of later operating systems such as VMS
>>> and Windows NT.
>>> ...
>>> RSX-11 began as a port to the PDP-11 architecture of the earlier
>>> RSX-15 operating system for the PDP-15 minicomputer, first released in
>>> 1971. The main architect for RSX-15 (later renamed XVM/RSX) was Dennis
>>> “Dan” Brevik.
>>> ...
>>> The porting effort first produced small paper tape based real-time
>>> executives (RSX-11A, RSX-11C) which later gained limited support for
>>> disks (RSX-11B). RSX-11B then evolved into the fully fledged RSX-11D
>>> disk-based operating system, which first appeared on the PDP-11/40 and
>>> PDP-11/45 in early 1973. The project leader for RSX-11D up to version
>>> 4 was Henry Krejci. While RSX-11D was being completed, Digital set out
>>> to adapt it for a small memory footprint giving birth to RSX-11M,
>>> first released in 1973. From 1971 to 1976 the RSX-11M project was
>>> spearheaded by noted operating system designer Dave Cutler, then at
>>> his first project. Principles first tried in RSX-11M appear also in
>>> later designs led by Cutler, DEC's VMS and Microsoft's Windows NT.
>>> </quote>
>>>
>>> https://en.wikipedia.org/wiki/PDP-15#RSX-15
>>>
>>> <quote>
>>> RSX-15 was released by DEC in 1971. The main architect for RSX-15
>>> (later renamed XVM/RSX) was Dennis "Dan" Brevik.
>>>
>>> Once XVM/RSX was released, DEC facilitated that "a PDP-15 can be
>>> field-upgraded to XVM" but it required "the addition of the XM15
>>> memory processor."
>>>
>>> The RSX-11 operating system began as a port of RSX-15 to the PDP-11,
>>> although it later diverged significantly in terms of design and
>>> functionality.
>>> </quote>
>>>
>>> All before my time.
>>>
>>> But I do remember that VAX and VMS VAX had some PDP-11 and RSX-11
>>> compatibility mode features.
>>>
>>> Arne
>>
>>
>> Thank you.  That takes me back a little bit further.  But I fear the
>> very origins, the driving model, may be long lost by this time.  I
>> have a number of very early textbooks on Operating Systems and none
>> of them describe features common in VMS or RSX.  It's really just
>> curiosity, but I wondered where some of the concepts originated.
>>
>> bill
>>
>
> Looking at it from a different perspective ....
>
> Back in 1974 I was introduced to a PDP11/40 running RSTS V04b.  At the
> time, the only supported language was Basic+, an interpreter.
>
> Where RSTS came from, I don't know, but what I was told was that David
> Hart of Evens, Griffith, and Hart wrote the original Basic+.  David is
> no longer with us, but, perhaps John Santos might have some information
> of the earlier days.
>
> While DEC ended up with RSTS and Basic+, what it seemed like to me is
> that the software people at DEC considered RSX as a proper OS and RSTS
> "that other thing".  Perhaps where their NIH started, or, perhaps they
> already embraced that concept.
>
> I wasn't a user of RSX at the time, so I really don't have any memories
> of it on the PDP11.
>
> Some time after 1974, don't know exactly when, DEC produced some type of
> RSX subsystem for RSTS, which allowed MACRO-11, and other RSX languages
> to run on RSTS.  These included BP2 (Basic Plus 2) which was a compiled
> version of Basic Plus.
>
> When VAX and VMS came along, VMS inherited much from RSX, as that seemed
> to be the preferred choice for the DEC software people.  VAX and VMS was
> aimed at the scientific market initially.  Only when DEC wanted into the
> business market did they start incorporating capabilities from RSTS,
> since RSTS was heavily used in the business market.
>
> So yeah, VMS was based initially on RSX, and later had RSTS capabilities
> added.  The result was something better than the sum of RSX and RSTS.
>
> I never heard any stories of where RSTS came from ...
>

I believe RSX and RSTE were predated by RT-11 which heavily influenced 
CP/M and later DOS. TSX-11 (which ran on RT-11) was considered a cheaper 
version of RSTS.

https://en.wikipedia.org/wiki/RT-11


Jeff