alt Hacker NewsThat's what I think too. The VAX is a lot more like the PDP-11 than the PDP-10. Hard core 36-bit PDP-10 programmers (like DIGEX, who I quoted in response to Walter's comment) were dismissive of and looked down on the 32 bit VAX.
Doug Humphrey's nickname was DIGEX, and he had a PDP-10 in his living room in Westchester Tower Apartments that he acquired from a loading dock at the University of Maryland. It was challenging to haul up in the elevator! It had two power cords, and two of us had to plug them in at the same time, into outlets on different circuits, so it got both hot legs.
He started one of the first ISPs by that name, which was later acquired by Worldcom:
https://en.wikipedia.org/wiki/Digex
The Digex Video! - Part 1:
https://www.youtube.com/watch?v=IsgROO4MIvc
DEF CON 12 - Doug Mohney, DIGEX At the Dawn of the Commercial Internet:
https://www.youtube.com/watch?v=uxMq-x9rlJM
The article also didn't mention the PDP-15, which was the fifth and last 18 bit DEC machine of the PDP-1 => 4 => 7 => 9 => 15 lineage.
That's right.
A lot of features of VAX and VMS are clearly inherited directly from PDP-11 and RSX-11M.
The main resemblances between VAX and PDP-10 are just that VAX is bigger and more powerful than PDP-11 and it is big enough and fast enough to be an upgrade even for PDP-10 not only from PDP-11.
Nonetheless there is something that VAX has inherited from PDP-10, but not really from the base DEC PDP-10 but from the enhancements that the users of PDP-10 had done to it.
The company BBN (Bolt Beranek and Newman Inc.) had made since 1970 a so-called "BBN Pager" for PDP-10, which was a hardware extension that added a paged memory management unit to PDP-10. They also designed the TENEX operating system for the PDP-10 extended with the BBN Pager.
The TENEX operating system is the origin of several very important innovations, like the memory-mapped files, which were later brought to UNIX by 4.2BSD, through SunOS 4.0 and 4.3BSD-Reno. Several of the earliest implementations of some Internet protocols, like Telnet and FTP, were done on computers running TENEX (i.e. extended PDP-10s). Implementing Telnet required the concept of pseudo-terminal, which was also imported in 4.2BSD and later the use of pseudo-terminals was expanded in various UNIX variants, to applications like terminal emulators in GUI desktops.
The paged memory management from which VAX got its name (Virtual Address Extension) comes directly from the BBN Pager extension of PDP-10.