||A VGA dummy plug is a simple hack to fool the GPU and Windows by let them thinking there is a monitor plugged on a card. This hack is useful in some situations where you have two or more graphics cards and need them to be active:|
The VGA dummy principle is simple: simulating the monitor RGB channels load with 3 resistors. Any resistor between 50 and 150 ohms is okay.
Here is the electronic scheme for a DVI connector:
Some interesting links: