I remember the thing called a Retrographics VT640 (I
think). It was an
add-on board that fitted inside a VT100 and which gave Tektronix
graphics. You still had the normal VT100 text display, which could be
overlayed on the graphics output.
I have one of these boards. If anybody wants it then let me know.
--
Kevan
Collector of old computers:
http://www.heydon.org/kevan/collection/