I recently wrote about how the X Window System didn't immediately have (thin client) X terminals . X terminals are now a relatively obscure part of history and it may not be obvious to people today why they were a relatively significant deal at the time. So today I'm going to add some additional notes about X terminals in their heyday, from their introduction around 1989 through the mid 1990s.

One of the reactions to my entry that I've seen is to wonder if there was much point to X terminals, since it seems like they should be close to much more functional normal computers and all you'd save is perhaps storage. Practically this wasn't the case in 1989 when they were introduced; NCD's initial models cost substantially less than, say, a Sparcstation 1 (also introduced in 1989), it appears less than half the cost of even a diskless Sparcstation 1. I believe that one reason for this is that memory was comparatively more expensive in those days and X terminals could get away with much, much less of it, since they didn't need to run a Unix kernel and enough of a Unix user space to boot up the X server (and I believe that some or all of the software was run directly from ROM instead of being loaded into precious RAM).

(The NCD16 apparently started at 1 MByte of RAM and the NCD19 at 2 MBytes, for example. You could apparently get a Sparcstation 1 with that little memory but you probably didn't want to use it for much.)

In one sense, early PCs were competition for X terminals in that they put computation on people's desks, but in another sense they weren't, because you couldn't use them as an inexpensive way to get Unix on people's desks. There eventually was at least one piece of software for this, DESQview/X , but it appeared later and you'd have needed to also buy the PC to run it on, as well as a 'high resolution' black and white display card and monitor. Of course, eventually the march of PCs made all of that cheap , which was part of the diminishing interest in X terminals in the later part of the 1990s and onward.

(I suspect that one reason that X terminals had lower hardware costs was that they probably had what today we would call a 'unified memory system', where the framebuffer's RAM was regular RAM instead of having to be separate because it came on a separate physical card.)

You might wonder how well X terminals worked over the 10 MBit Ethernet that was all you had at the time. With the right programs it could work pretty well, because the original approach of X was that you sent drawing commands to the X server, not rendered bitmaps . If you were using things that could send simple, compact rendering commands to your X terminal, such as xterm, 10M Ethernet could be perfectly okay. Anything that required shipping bitmapped graphics could be not as impressive, or even not something you'd want to touch, but for what you typically used monochrome X for between 1989 and 1995 or so, this was generally okay.

(Today many things on X want to ship bitmaps around, even for things like displaying text. But back in the day text was shipped as, well, text, and it was the X server that rendered the fonts.)

When looking at the servers you'd need for a given number of diskless Unix workstations or X terminals, the X terminals required less server side disk space but potentially more server side memory and CPU capacity, and were easier to administer. As noted by some commentators here , you might also save on commercial software licensing costs if you could license it only for your few servers instead of your lots of Unix workstations. I don't know how the system administration load actually compared to a similar number of PCs or Macs, but in my Unix circles we thought we scaled much better and could much more easily support many seats (and many potential users if you had, for example, many more students than lab desktops).

My perception is that what killed off X terminals as particularly attractive, even for Unix places, was that on the one hand the extra hardware capabilities PCs needed over X terminals kept getting cheaper and cheaper and on the other hand people started demanding more features and performance, like decent colour displays. That brought the X terminal 'advantage' more or less down to easier administration, and in the end that wasn't enough (although some X terminals and X 'thin client' setups clung on quite late, eg the SunRay , which we had some of in the 2000s).

Of course that's a Unix centric view. In a larger view, Unix was displaced on the desktop by PCs, which naturally limited the demand for both X terminals and dedicated Unix workstations ( which were significantly marketed toward the basic end of Unix performance , and see also ). By no later than the end of the 1990s, PCs were better basic Unix workstations than the other options and you could use them to run other software too if you wanted to, so they mostly ran over everything else even in the remaining holdouts.

( We ran what were effectively X terminals quite late, but the last few generations were basic PCs running LTSP not dedicated hardware. All our Sun Rays got retired well before the LTSP machines.)

(I think that the 'personal computer' model has or at least had some significant pragmatic advantages over the 'terminal' model, but that's something for another entry.)