ATI Catalyst Drivers & Windows Vista

Andrew Dodd of ATI has passed along a marketing brief/white paper on Window Vista’s new graphics driver model (WDDM) that shows off enhancements that ATI has made to the Vista driver. Probably most notable to 3D graphics cards users is this: less crashing by design. w00t!!1 The full 1MB zipped PDF can be downloaded here.

The biggest change in the WDDM is that much of the graphics driver has been moved from kernel space to user space. The major goal of this change is to isolate the graphics driver and its activities as much as possible from the operating system (and other applications). The WDDM has two major components, but with slightly different names - the User Mode Driver (UMD) and the Kernel Mode Driver (KMD). See Figure 6 for a high level diagram of the ATI Windows Vista driver model. The ATI Windows Vista graphics driver consists of multiple User Mode Drivers (UMDs); Direct3D and OpenGL for 3D graphics and DXVA for video functionality. Support for 2D in the graphics driver is no longer needed as the Windows Vista desktop is drawn using the Direct3D API. The UMDs are completely isolated from the kernel mode driver and the graphics hardware. The Windows Vista operating system loads a separate copy of the UMD for each application. In the unlikely event that an application or its UMD does something illegal and causes an error, only that single application will close, leaving the Windows Vista operating system unscathed, allowing the user to continue working.

The Kernel Mode Driver (KMD) is the interface between the graphics driver and the graphics hardware. The most important change in the WDDM is that the kernel mode driver framework is not as closely linked to the operating system as it is in the XPDM. This means that there is a far less chance of the operating system encountering an issue, in the unlikely event of a KMD error.

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