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Author: QuadiblocQuadibloc Date: Dec 31, 2007 09:45
I was astounded, as I recently noted, to learn from Gordon Bell's
"Computer Engineering" that the PDP-9 was a microprogrammed machine.
The PDP-4/7/9/15 architecture involved a very simple instruction set.
If anything, the PDP-15 gave the appearance of being an enlarged
version of the PDP-8.
Thus, back in the 1970s, I had wondered - since the PDP-8 was so
cramped that it didn't have even a proper load and store instruction,
but made do with TAD and DCA, why DEC didn't make machines with the
PDP-15 architecture, priced at half again as much as a PDP-8, and make
some effort to migrate users to that, because, clearly, a
straightforwards machine would offer more for the money than one that
was cramped.
But since then, I've learned a few things.
One of them is that a bare-bones PDP-15 cost $15,500, which was close
to half again the price of a PDP-8/e, despite coming in a bigger box.
Another is that DEC had made an effort to bring that architecture to
people at a lower price; the PDP-9/L shows how hard they tried.
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Author: Al KossowAl Kossow Date: Dec 31, 2007 10:14
Quadibloc wrote:
> If DEC
> needed a lot of additional programmers and engineers in a hurry to
> take the VAX where they wanted it to go, the quickest way to obtain
> them would be internally.
Melinda Varian's history of CMS
http://www.princeton.edu/~melinda/25paper.pdf
notes that there was a large layoff of IBM programmers in the mid 70's
as they transferred CMS development to NY.
I had heard that there was a large influx of IBM influence in the mid
70's at DEC. Was this one of the sources?
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Author: Mark CrispinMark Crispin Date: Dec 31, 2007 11:13
On Mon, 31 Dec 2007, Quadibloc posted:
> Had the PDP-15 come out after the PDP-11/20, it would have been clear
> that it was simply there to provide existing users with an upgrade
> path, instead of being a new and exciting machine in its own right.
The 18-bit machines had become obscure even in the early 1970s. PDP-8/e,
PDP-10 (KA10, KI10), and various form of PDP-11 were uniquitous, but PDP-9
and PDP-15 were machines that were heard of, but rarely (or never) seen.
The first 18-bit machine that I saw was the PDP-1 at MIT in 1976, and by
that time it was ancient. My next encounter was with a PDP-15 at Stanford
in 1977.
> The importance of the PDP-11 in the early development of UNIX, and in
> much other innovative work with minicomputers, can hardly be
> overstated.
Indeed.
> Well, it *was* always VAXes, and never DECsystem-20s, that Russian
> spies kept trying to smuggle out of the Free World. They may have
> known something.
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Author: Anne & Lynn WheelerAnne & Lynn Wheeler Date: Dec 31, 2007 12:39
Al Kossow spies.com> writes:> Melinda Varian's history of CMS
> http://www.princeton.edu/~melinda/25paper.pdf
>
> notes that there was a large layoff of IBM programmers in the mid 70's
> as they transferred CMS development to NY.
>
> I had heard that there was a large influx of IBM influence in the mid
> 70's at DEC. Was this one of the sources?
the actual situation was that in the wake of cancelling future
system project
http://www.garlic.com/~lynn/subtopic.html#futuresys
there were mad rush to try and get stuff back into the 370 product
pipeline. the favorite son operating system group in POK managed to
convince the corporation that it needed all of the vm370/cms developers
up in burlington mall ... in order to make the mvs/xa schedule; aka
kill/terminate the vm370/cms product and transfer everybody from the
burlington development group to POK to support mvs/xa development.
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Author: QuadiblocQuadibloc Date: Dec 31, 2007 13:15
On Dec 31, 12:13Â pm, Mark Crispin CAC.Washington.EDU> wrote:> Digital failed, repeatedly, to build a viable follow-on processor to the
> KL10. Â Both Jupiter (2080/4050) and Venus (VAX 8600) projects were in deep
> trouble for multiple reasons, a great many of which were in management.
>
> I heard that Alan Kotok was called in to straighten up the mess, and he
> came back with an ultimatum: pick which one to save because he'd only be
> able to save one. Â The decision was to save Venus.
>
> The Jupiter instruction set architecture was quite nice and very well
> thought-out; in reviewing it today, my favorable impressions are renewed.
> However, the hardware in the lab was a mess. Â I heard rumors of boards
> with 50+ ECOs made to them.
I had noticed a mention of Dolphin and Minnow on the Columbia
University web site.
If Jupiter had been 80%% - 90%% complete, and hadn't had serious
problems, then, of course, cancelling it would have been an irrational
decision.
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Author: Carl AppellofCarl Appellof Date: Dec 31, 2007 16:26
> Could DEC have copied IBM, which allowed some models of the System/360
> line to emulate the 7094-II? The VAX was microcoded, after all.
>
The VAX 11/780 could run PDP-11 code natively, as well as running VAX code.
THAT is the market DEC was trying to protect at the time - PDP-11 users that
wanted to move up from 11/70s. It was all altruism either. In the early
releases of VMS, many of the command line utilities still ran from MCR via
the RSX-11 subsystem.
I think it would have been tough, even in microcode, to emulate a 36-bit
machine with a 32-bit architecture.
Carl
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Author: QuadiblocQuadibloc Date: Dec 31, 2007 16:56
On Dec 31, 5:26 pm, "Carl Appellof" yahoo.com> wrote:> "Quadibloc" wrote in message
>
>> Could DEC have copied IBM, which allowed some models of the System/360
>> line to emulate the 7094-II? The VAX was microcoded, after all.
>
> The VAX 11/780 could run PDP-11 code natively, as well as running VAX code.
> THAT is the market DEC was trying to protect at the time - PDP-11 users that
> wanted to move up from 11/70s.
And that I understand. The VAX was a higher priority; it served both a
larger market, and one more likely to sustain the customer in the
future, and one with more growth possibilities.
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Author: John ByrnsJohn Byrns Date: Dec 31, 2007 17:09
In article ,
"Carl Appellof" yahoo.com> wrote:
>> Could DEC have copied IBM, which allowed some models of the System/360
>> line to emulate the 7094-II? The VAX was microcoded, after all.
>>
>
> The VAX 11/780 could run PDP-11 code natively, as well as running VAX code.
> THAT is the market DEC was trying to protect at the time - PDP-11 users that
> wanted to move up from 11/70s.
But the VAX 11/780 wasn't a move up from the 11/70 in performance. We
moved from an 11/70 to an 11/780, and the 11/780 didn't match the
performance of the 11/70, of course the 11/70 had serious limitations on
the size of programs that could be run and the 11/780 certainly fixed
that problem.
Regards,
John Byrns
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Author: Anne & Lynn WheelerAnne & Lynn Wheeler Date: Dec 31, 2007 17:26
Anne & Lynn Wheeler garlic.com> writes:> quite a few of the people in the burlington group didn't leave the area
> ... and got jobs at various places like dec, prime, etc. some number
> showed up in the vms group.
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Author: Brian InglisBrian Inglis Date: Dec 31, 2007 21:40
>The importance of the PDP-11 in the early development of UNIX, and in
>much other innovative work with minicomputers, can hardly be
>overstated.
The importance of the PDP-7 running the first edition of Unix written in
assembler is rarely mentioned.
--
Thanks. Take care, Brian Inglis Calgary, Alberta, Canada
Brian.Inglis@ CSi.com (Brian[dot]Inglis{at}SystematicSW[dot]ab[dot]ca)
fake address use address above to reply
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