Apparently by shorting the pins, the video card will report that there is an unknown external display attached.

The DE-9 connector (above) used for CGA, MDA, and Hercules cards, and DE-15 connector (below) used for VGA In 1987, IBM defined a new graphics standard to push the graphics on their PC to levels ...

A graphics card (display adapter) that provides VGA resolution. Most PC graphics cards provide base level VGA resolutions even if they do not provide the actual VGA connector. See VGA. THIS ...

A feature of a high-resolution graphics card that does not support standard VGA resolution. The VGA card in the computer is cabled to the pass-through circuit on the high-res adapter. When high ...