Selects the amount to scale the display on the first pass. There is an Auto preset as well as presets for fixed 1x, 2×1, 2x, 3x, and 4x ratios. In addition, a ratio can manually be set anywhere from 0.25×0.25 to 16×16. The Auto preset will automatically double pixels horizontally if the horizontal resolution is 400 pixels or less, and will double pixels vertically if the vertical resolution is 300 or less.
In addition, if Video mode is set to Change desktop resolution and Add extra display modes is enabled, a subset of low resolution pixel doubled modes will be added, providing support for low resolution modes even if not supported by your graphics card.
If Primary buffer scaling is set to Scale to screen, typing 0.5 in the box will enable 2×2 supersampling for Direct3D applications. This will also modify the behavior of “Change desktop resolution” in the Display tab.