HP Vectra XU5 Reference Manual page 64

VESA Connector
The Video Electronics Standards Association (VESA) defines a standard video connector
variously known as the VESA feature connector, auxiliary connector, or pass-through
connector. The HP Vectra XU supports an output-only VESA feature connector. This
connector is integrated on the system board (or on the Matrox MGA II PCI Video board) and
is connected directly to the pixel data bus and the synchronization signals.
To ensure synchronization of colors between the integrated video controller and a second
PCI video controller on an accessory board, a snooping utility is employed to communicate
color-synchronization information to the PCI accessory board via the VESA feature
connector.
Vectra XU Technical Reference The Integrated Ultra VGA Controller 64