From: D. Hugh Redelmeier via Talk <talk@lists.gtalug.org>
By the time that "glass TTYs" came on the scene, ICs were available and other forms of memory were used. I remember getting a large shift-register memory from a Datapoint terminal (the Intel 8008 architecture matches the Datapoint 2200's processor).
Here's the Wikipedia article on teh Datapoint 3300, "one of the first glass TTYs". The article goes into more detail about shift-registers being used as the screen memory. Shift registers are a lot simpler than RAM. There's no addressing logic. There are no address pins. (I always thought that SPARC's register windows could have taken a lot less resources if were implemented with shift registers. There was no need to support random access for non-current windows.)