I have a mid-1980s CRT monitor, a C. Itoh Chroma Pro CM1000, with an 8-pin DIN RGB input that's visually similar to the digital RGB input on a Commodore 1084. The input is selectable between "RGB," "RGBI," and "XRGB."
Presumably "RGBI" is an RGB + intensity digital signal, i.e., CGA. But what are "RGB" and "XRGB?"
I'm guessing that "RGB" is probably digital RGB but without the intensity signal, but I'm totally mystified about what "XRGB" might be.