Our system was based on the Q-BUS DEC LSI-11 that ran the RT-11 OS.
These systems would find the most efficient way to make connections between electronic components on a PCB. The resulting Gerber files were then sent off to a service that would convert the files into actual multi-layered printed circuit boards.
We interacted with the DEC via VT-101 terminal but the PCB designers used a mouse and a crude but hugely heavy color CRT. I don't recall what the color graphics subsystem was comprised of. I think it may have been proprietary.
