VGA-Compatible, x86-Based Miniports

Self-declared “VGA-compatible” miniport drivers are set up to configure themselves in the registry with VgaCompatible set to one (TRUE). VGA-compatible miniport drivers have the following features:

• Such a miniport driver, usually of an SVGA adapter, is based on the system-supplied VGA miniport driver, with code modified to support adapter-specific features. The system-supplied VGA display drivers use the kernel-mode support provided by VGA-compatible miniport drivers, so the developer of a new miniport for a VGA-compatible adapter need not write a new display driver.

• Such a miniport driver both provides support for full-screen MS-DOS® applications to do I/O directly to the adapter registers and also functions as a video validator to prevent such an application from issuing any sequence of instructions that would hang the machine.

Miniport drivers of most SVGA adapters fall in this category, but any new miniport driver for a nonSVGA adapter can provide VGA compatibility support at the discretion of the driver designer.