free and open-source device drivers for graphic chipsets are "stewarded" by Mesa (because the existing free and open-source implementation of APIs are developed inside of Mesa). Currently there are two frameworks to write graphics drivers: "classic" and Gallium3D. An overview over some (but not all) of the drivers available in Mesa is given at . There are device drivers for AMD/ATI R100 to R800, Intel, and Nvidia cards with 3D acceleration. Previously drivers existed for the IBM/Toshiba/Sony Cell processor of the PlayStation 3, S3 Virge & Savage chipsets, VIA chipsets, Matrox G200 & G400, and more. The free and open-source drivers compete with proprietary closed-source drivers. Depending on the availability of hardware documentation and man-power, the free and open-source driver lag behind more or less in supporting 3D acceleration of new hardware. Also, 3D rendering performance was usually significantly slower with some notable exceptions. Today this is still true for Nouveau for most NVIDIA GPUs while on AMDs Radeon GPUs the open driver now mostly matches or exceeds the proprietary driver's performance. Direct Rendering Infrastructure (DRI) At the time 3D graphics cards became more mainstream for PCs, individuals partly supported by some companies began working on adding more support for hardware-accelerated 3D rendering to Mesa. The Direct Rendering Infrastructure (DRI) was one of these approaches to interface Mesa, OpenGL and other 3D rendering API libraries with the device drivers and hardware. After reaching a basic level of usability, DRI support was officially added to Mesa. This significantly broadened the available range of hardware support achievable when using the Mesa library. With adapting to DRI, the Mesa library finally took over the role of the front end component of a full scale OpenGL framework with varying backend components that could offer different degrees of 3D hardware support while not dropping the full software rendering capability. The total system used many different software components. While the design requires all these components to interact carefully, the interfaces between them are relatively fixed. Nonetheless, as most components interacting with the Mesa stack are open source, experimental work is often done through altering several components at once as well as the interfaces between them. If such experiments prove successful, they can be incorporated into the next major or minor release. That applies e.g. to the update of the DRI specification developed in the 2007-2008 timeframe. The result of this experimentation, DRI2, operates without locks and