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

Paul Koning paulkoning at
Thu Feb 11 13:54:09 CST 2016

> On Feb 11, 2016, at 2:48 PM, Rich Alderson <RichA at> 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 
>>> 780.) 
>> Any idea about the date of when VMS could do that with a VAX?
> From the very beginning?  That is, 25 October 1977?
> 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).

Indeed.  RSTS/E did better, with less hardware -- 64 users on an 11/70 was no problem, and earlier on you could run 16 users on an 11/20 (though not all that comfortably).  


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