The present invention relates to Basic Input/Output System (BIOS). More particularly, the invention relates to enabling video BIOS and display drivers to leverage system BIOS platform abstract.
Many of the Graphics Memory Controller Hub (GMCH) configuration control registers, affecting graphics and graphics memory, are in the system dynamic random-access memory (DRAM) controller device. Moreover, the graphics interface is assigned as Device#2 while the system memory controller is assigned as Device#0, which is owned by system Basic Input/Output System (BIOS) and system bus drivers. However, in Plug-n-Play (PnP) operating systems, such as Windows 2000, graphics drivers are not permitted to access registers or resources not in the drivers' scope of ownership or declared PnP configuration space. Accordingly, in integrated and/or embedded graphics platforms, the platform-specific information is often accessed via the video BIOS communicating with the system BIOS. This communication utilizes private Int15h calls (i.e. interrupts).
However, the Windows display drivers cannot invoke the Int15h real-mode handler from within the operating system. Moreover, the display drivers cannot use the video BIOS when internal graphics is configured as a non-Video Graphics Array (non-VGA) display adapter. Thus, the legacy VGA video BIOS is not available when the adapter is secondary to either a Peripheral Component Interconnect (PCI) or Accelerated Graphics Port (AGP) VGA adapter.