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The display driver model from Windows 8.1 and Windows Phone have converged into a unified model for Windows 10. [43] A new memory model is implemented that gives each GPU a per-process virtual address space. Direct addressing of video memory is still supported by WDDMv2 for graphics hardware that requires it, but that is considered a legacy case.
A GART is used as a means of data exchange between the main memory and video memory through which buffers (i.e. paging/swapping) of textures, polygon meshes and other data are loaded, but can also be used to expand the amount of video memory available for systems with only integrated or shared graphics (i.e. no discrete or inbuilt graphics ...
Much the way the system BIOS provides a set of functions that are used by software programs to access the system hardware, the video BIOS provides a set of video-related functions that are used by programs to access the video hardware as well as storing vendor-specific settings such as card name, clock frequencies, VRAM types & voltages.
Video memory was shared with the first 128 KiB of RAM. The exact size of the video memory could be reconfigured by software to meet the needs of the current program. An early hybrid system was the Commodore Amiga which could run as a shared memory system, but would load executable code preferentially into non-shared "fast RAM" if it was available.
Network device drivers for Windows XP use NDIS 5.x and may work with subsequent Windows operating systems, but for performance reasons network device drivers should implement NDIS 6.0 or higher. [8] Similarly, WDDM is the driver model for Windows Vista and up, which replaces XPDM used in graphics drivers.
Higher performance hardware such as graphics cards use DMA to access memory directly; in a virtual environment all memory addresses are re-mapped by the virtual machine software, which causes DMA devices to fail. The IOMMU handles this re-mapping, allowing the native device drivers to be used in a guest operating system.
The amount of video memory is dependent upon the amount of pre-allocated video memory plus DVMT allocation. DVMT, as its name implies, dynamically allocates system memory for use as video memory to ensure more available resources for 2D/3D graphics performance, e.g. for graphically demanding games.
When a user-space program needs a chunk of video memory (to store a framebuffer, texture or any other data required by the GPU [15]), it requests the allocation to the DRM driver using the GEM API. The DRM driver keeps track of the used video memory and is able to comply with the request if there is free memory available, returning a "handle ...