The VC8-E point plot control board set was used to drive X/Y deflection monitors like the VR14 and CRT type displays. The VC8-E generated the display by the processor specifying an 10 bit X and Y location and then requesting that a spot be drawn on the CRT at that location. It then repeated this process to draw the entire display with out of a bunch of dots. On the VR14 link above are pictures and videos of the display.
Two types of displays were supported by this board set, the X/Y CRT like the VR14 which required the entire display to be refreshed at greater than 30-60Hz rate to prevent flicker. It could also drive storage CRT's like the Tektronix 4002 storage display or 611 storage scopes. This type of display stored picture in a special CRT so they did not need to be refreshed. This allowed generation of more complex pictures without flicker but the entire display could only be erased at once so dynamic displays were not possible.
The VC8E controller cost $1185 and for $100 installation from DEC in 1974. Maintenance was $11 per month.
Link to pictures of VC8-E controller
VC8-E Programming information