[Info-vax] OS Ancestry

[Dave Froble]

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 ...

-- 
David Froble                       Tel: 724-529-0450
Dave Froble Enterprises, Inc.      E-Mail: davef at tsoft-inc.com
DFE Ultralights, Inc.
170 Grimplin Road
Vanderbilt, PA  15486