[Info-vax] For sale: VAXstation 4000/90 128MB Fully Working and Tested

[j...@ieee.org]

On Monday, July 4, 2022 at 5:30:34 PM UTC-5, Johnny Billquist wrote:
...
> There was definitely a demand for faster PDP-11s up to a point. But 
> somewhere along the way, it became a non-issue as the effort in 
> developing ever larger software solutions on the PDP-11 became a huge 
> effort in just fitting it into the address space. And so large, complex 
> software development moved away from the PDP-11 to the successor - VAX. 
> But the PDP-11 didn't die because of that. It just became a little more 
> limited in what customers used it for, and for that, the speed was 
> already acceptable. As was the other parameters. 
> The one thing asked for later in life was improvements in tools and 
> networking, and reduction of price. 
> 
> Demand for faster CPUs exists also today. But we've sortof hit a wall 
> for single CPU speeds, so now we're mainly adding more and more cores.
> 
> Johnny
...

It was clear to many of us doing real-time acquisition that the PDP-11 cpu and bus(es) had run their course as well.  We looked at VAX offerings (rtVAX) and it was apparent our cost, OS (RT-32 anyone?) cpu/address and bus/device needs were not going to be satisfied.  Most of the analysis code was in a semi-portable language, so that wasn't a limiting factor.  We were prepared to rewrite the time or performance critical code to another system.    The 68xxx series resembled the PDP-11 instruction approach in some ways and took a some share of this niche.  Dedicated microcontrollers took the rest.

   Jerry