First of all, it's GPX, not GFX. The only difference from MicroVAX II is
an extra card - a 4- or 8-plane 1024x864 graphics adapter. All the rest
is EXACTLY the same. Disabling graphics amounts to yanking the adapter
out of the box (this is 2 boards for a 4-plane option, 3 boards for
a 8-plane one). On powerup, the CPU self-test checks for the presence
of the graphics board, and, if it is there, uses it as the display
device. If it is not there, it uses the serial channel built into the
CPU board (it is the DB9 connector on the CPU's patch panel on the rear,
next to two rotary knobs and a switch).

Tony Konashenok