A couple of years after Athena got going the Andrew project at CMU got started.  That project focused primarily on early Sun workstations.  There was some fooling around with some sort of Unix on the PC/AT, but the lack of virtual memory support and the weakness of the networking cards for the machine meant that we never saw them.

My memory of how X evolved is a bit confused, but there was a collaboration between Athena and Andrew.  Each had built window systems independently.  My recollection is that Gosling, Rosenthal, and Sidebotham built the core of the CMU one.  It introduced the separation between the display engine (the ‘server’) and the application (the ‘client’) using an ancestor of the X Protocol.

After a while a consolidated window system was agreed, using front end ideas from the MIT W system and the CMU wm system and preserving the X Protocol.  This produced a flexible architecture that allowed an application to run anywhere and display in a window anywhere else.  It also made networking support a must.

On Wed, Jan 25, 2023 at 2:54 PM Theodore Ts'o <tytso@mit.edu> wrote:
On Wed, Jan 25, 2023 at 11:41:12AM -0500, Rich Salz wrote:
> > Aa for the questions of the UNIX-ness of X, it started in Athena, which as
> > I understand it was supposed to be relatively OS-agnostic distributed
> > computing? In any case, the predecessor ran on a different OS, not sure how
> > significant that is to the genesis of what would be called X or what OS it
> > "started" on.
> Athena was about scaling up Unix workstations. It was started with grants
> from IBM and Digital. It was never OS-agnostic.

Well..... technically Athena was about computing in higher ed.  If you
go far back enough, at the very beginning, we used VAX 750's and IBM
PC/AT's running DOS.  As soon as the Microvax 2's and IBM PC/RT's came
in, about 2 or so years in, Project Athena switched to Unix
workstations, but in the earliest days (which would have been pre-X
Windows), Project Athena had not yet standardized on Unix or
workstations for that matter.

The VAX 750's were huge time-sharing systems that you could connect to
via VT-100's and VS-100 that were hard-wired to the VAX 750's, and
telnet from IBM PC/AT's.  The smaller clusters used PC/AT's because
they were more flexible as to which 750 you were connecting to;
otherwise, undergraduates had to go to the right terminal room in the
right part of campus to connect to the Vax 750 that you were assgined
to based on the starting character of your last name.  (And graduate
students initially didn't have access to Project Athena at all;
although if you were in EECS, LCS or the AI Lab you had access to
dedicated systems, of course.)

One of the perks for being hired as a student systems programmer back
then was that you got accounts on all of the Vax 750's, so you could
use any terminal room across campus.  :-) We then would either rlogin
to our "home" Vax 750, or we had scripts that would replicate our home
directories across the various 750's.

There was a brief, shining moment that we were standardized on
BSD-derived Unix systems, but then IBM turned down AOS (the "academic"
operating system), and we were forced to use AIX on the IBM RT's, with
all that this implied: SMIT, and other horrors.

"AIX: it *reminds* you of Unix...." was the saying at the time ---
although we tried not to say that when the IBM engineers assigned
Athena were in hearing range :-).  The one saving grace of the IBM
RT's was that they were three MIPS machines, while the Microvax's were
but a single MIPS, and that made a huge different if you were running
TeX or LaTeX.


                                                - Ted