Appendix T. Support for GLX in Xinerama
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## Appendix T. Support for GLX in Xinerama

This driver supports GLX when Xinerama is enabled on similar GPUs. The Xinerama extension takes multiple physical X screens (possibly spanning multiple GPUs), and binds them into one logical X screen. This allows windows to be dragged between GPUs and to span across multiple GPUs. The NVIDIA driver supports hardware accelerated OpenGL rendering across all NVIDIA GPUs when Xinerama is enabled.

To configure Xinerama: configure multiple X screens (please refer to the XF86Config(5x) or xorg.conf(5x) manpages for details). The Xinerama extension can be enabled by adding the line

        Option "Xinerama" "True"

to the "ServerFlags" section of your X config file.

Requirements:

- It is recommended to use identical GPUs. Some combinations of non-identical, but similar, GPUs are supported. If a GPU is incompatible with the rest of a Xinerama desktop then no OpenGL rendering will appear on the screens driven by that GPU. Rendering will still appear normally on screens connected to other supported GPUs. In this situation the X log file will include a message of the form:

      (WW) NVIDIA(2): The GPU driving screen 2 is incompatible with the rest of
      (WW) NVIDIA(2):      the GPUs composing the desktop.  OpenGL rendering will
      (WW) NVIDIA(2):      be disabled on screen 2.

- The NVIDIA X driver must be used for all X screens in the server.

- Only the intersection of capabilities across all GPUs will be advertised.

- X configuration options that affect GLX operation (e.g.: stereo, overlays) should be set consistently across all X screens in the X server.

Known Issues:

- Versions of XFree86 prior to 4.5 and versions of X.Org prior to 6.8.0 lack the required interfaces to properly implement overlays with the Xinerama extension. On earlier server versions mixing overlays and Xinerama will result in rendering corruption. If you are using the Xinerama extension with overlays, it is recommended that you upgrade to XFree86 4.5, X.Org 6.8.0, or newer.

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