VAXen and minimal memory (was Re: The PDP11/04 has landed..)

Jerome H. Fine jhfinedp3k at
Thu Feb 11 19:39:32 CST 2016

 >Rich Alderson wrote:

>From: Jerome H. Fine
>Sent: Thursday, February 11, 2016 8:56 AM
>>>Jon Elson wrote:
>>>We paid somewhere between 200 and 250K for our first 11/780.  We had 
>>>an RM05 and a TU77, and 256 KB of memory.  It was a pretty basic 
>>>system, but ran rings around the campus 360/65 system.  We also had a 
>>>pair of 370/145's that were an expensive joke.  (The 360/65 ran rings 
>>>around BOTH of them.  They ran time sharing on them, limited to 4 
>>>users/machine.  We often had 8+ users plus batch jobs running on our 
>>Any idea about the date of when VMS could do that with a VAX?
>From the very beginning?  That is, 25 October 1977?
Since your answer seems to be an unstated question, I will attempt to
answer what you might have inferred.  I was just attempting to note that
the CDC 3300 hardware was able to support that function more than a
DECADE earlier.  By 1967 when I arrived, the system had already been
running for quite a while in support of many engineers who required access
to a computer that avoided the punch card route followed by submitting
the cards to the batch queue - and waiting - and waiting.

Access to an editor to compose the file followed by immediate placement
into the job queue was a huge improvement in the mid 1960s.

>VMS was built from the get-go as a timesharing operating system with a
>virtual memory architecture.  It was not the best of such, nor was the
>hardware done particularly well (a VM system with no Page-Modified bit
>in hardware? seriously???), but it was certainly capable of handling
>that many users (and more, depending on job mix).
Agreed!  But when you discuss the VAX and VMS, that is a decade later.
As long as the Cyber 3300 was able to get the job done in 1966, then a
quibble over implementation more than 10 years earlier seems a bit silly.

>So what was your question, really?
I did not have a question!  You made your answer into a question
with your TWO question marks.

>[1] Other timesharing systems existed, yes, but they were RPQ add-ons to
>    standard batch-oriented hardware.  Timesharing was built in on the PDP-6
>    factory floor.
If by factory floor, you mean where the hardware was built, then based
on 55 years of developing programs, I disagree.  "Timesharing", in my
opinion, is a result of the operating system software.  For example,
RT-11 running on a PDP-11/73 (or faster CPU) is certainly NOT
designed to be a timesharing operating system, although under very
specific conditions it can operate in that manner.  TSX-Plus will
execute on the identical hardware and have excellent performance
as a true timesharing operating system.

But the PDP-11 did not become the powerful computer that it
eventually became until at least about 1980.  When RSTS/E was
combined with that level of hardware, it was able to support
timesharing as well.  At this point when it is possible to run
RSTS/E on hardware that runs 100 times as fast as a PDP-11/93,
staying with RSTS/E makes sense for applications that are still
basically the same after 30 years.

So, back to my original statement which comments on much praising
of a VAX supporting editing sessions (along with running the programs
which were produced) around the mid 1970s.  I doubt that the original
1.0 VMS handled timesharing very well.  So I don't believe it was
unreasonable to make a statement that the same functions were available
more than a DECADE previously on a Cyber 3300 even though, as
you point out, the operating system in the mid 1960s was probably still
at the level of RT-11 as opposed to TSX-Plus.

I don't remember if the Cyber 3300 hardware even survived more than
10 years, but I suspect if it did, then by the mid 1970s it would have also
evolved into something that was much better than 10 years earlier.

Jerome Fine

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