Chapter 9. Known Issues
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## Chapter 9. Known Issues

The following problems still exist in this release and are in the process of being resolved.

Known Issues

Notebooks

  If you are using a notebook see the "Known Notebook Issues" in Chapter 16, Configuring a Notebook.

Texture seams in Quake 3 engine

  Many games based on the Quake 3 engine set their textures to use the `GL_CLAMP` clamping mode when they should be using `GL_CLAMP_TO_EDGE`. This was an oversight made by the developers because some legacy NVIDIA GPUs treat the two modes as equivalent. The result is seams at the edges of textures in these games. To mitigate this, older versions of the NVIDIA display driver remap `GL_CLAMP` to `GL_CLAMP_TO_EDGE` internally to emulate the behavior of the older GPUs, but this workaround has been disabled by default. To re-enable it, uncheck the "Use Conformant Texture Clamping" checkbox in nvidia-settings before starting any affected applications.

FSAA

  When FSAA is enabled (the __GL_FSAA_MODE environment variable is set to a value that enables FSAA and a multisample visual is chosen), the rendering may be corrupted when resizing the window.

libGL DSO finalizer and pthreads

  When a multithreaded OpenGL application exits, it is possible for libGL's DSO finalizer (also known as the destructor, or "_fini") to be called while other threads are executing OpenGL code. The finalizer needs to free resources allocated by libGL. This can cause problems for threads that are still using these resources. Setting the environment variable "__GL_NO_DSO_FINALIZER" to "1" will work around this problem by forcing libGL's finalizer to leave its resources in place. These resources will still be reclaimed by the operating system when the process exits. Note that the finalizer is also executed as part of dlclose(3), so if you have an application that dlopens(3) and dlcloses(3) libGL repeatedly, "__GL_NO_DSO_FINALIZER" will cause libGL to leak resources until the process exits. Using this option can improve stability in some multithreaded applications, including Java3D applications.

Thread cancellation

  Canceling a thread (see pthread_cancel(3)) while it is executing in the OpenGL driver causes undefined behavior. For applications that wish to use thread cancellation, it is recommended that threads disable cancellation using pthread_setcancelstate(3) while executing OpenGL or GLX commands.

This section describes problems that will not be fixed. Usually, the source of the problem is beyond the control of NVIDIA. Following is the list of problems:

Problems that Will Not Be Fixed

NV-CONTROL versions 1.8 and 1.9

  Version 1.8 of the NV-CONTROL X Extension introduced target types for setting and querying attributes as well as receiving event notification on targets. Targets are objects like X Screens, GPUs and Quadro Sync devices. Previously, all attributes were described relative to an X Screen. These new bits of information (target type and target id) were packed in a non-compatible way in the protocol stream such that addressing X Screen 1 or higher would generate an X protocol error when mixing NV-CONTROL client and server versions.

  This packing problem has been fixed in the NV-CONTROL 1.10 protocol, making it possible for the older (1.7 and prior) clients to communicate with NV-CONTROL 1.10 servers. Furthermore, the NV-CONTROL 1.10 client library has been updated to accommodate the target protocol packing bug when communicating with a 1.8 or 1.9 NV-CONTROL server. This means that the NV-CONTROL 1.10 client library should be able to communicate with any version of the NV-CONTROL server.

  NVIDIA recommends that NV-CONTROL client applications relink with version 1.10 or later of the NV-CONTROL client library (libXNVCtrl.a, in the nvidia-settings-319.32.tar.bz2 tarball). The version of the client library can be determined by checking the NV_CONTROL_MAJOR and NV_CONTROL_MINOR definitions in the accompanying nv_control.h.

  The only web released NVIDIA FreeBSD driver that is affected by this problem (i.e., the only driver to use either version 1.8 or 1.9 of the NV-CONTROL X extension) is 1.0-8756.

CPU throttling reducing memory bandwidth on IGP systems

  For some models of CPU, the CPU throttling technology may affect not only CPU core frequency, but also memory frequency/bandwidth. On systems using integrated graphics, any reduction in memory bandwidth will affect the GPU as well as the CPU. This can negatively affect applications that use significant memory bandwidth, such as video decoding using VDPAU, or certain OpenGL operations. This may cause such applications to run with lower performance than desired.

  To work around this problem, NVIDIA recommends configuring your CPU throttling implementation to avoid reducing memory bandwidth. This may be as simple as setting a certain minimum frequency for the CPU.

  Depending on your operating system and/or distribution, this may be as simple as writing to a configuration file in the /sys or /proc filesystems, or other system configuration file. Please read, or search the Internet for, documentation regarding CPU throttling on your operating system.

VDPAU initialization failures on supported GPUs

  If VDPAU gives the VDP_STATUS_NO_IMPLEMENTATION error message on a GPU which was labeled or specified as supporting PureVideo or PureVideo HD, one possible reason is a hardware defect. After ruling out any other software problems, NVIDIA recommends returning the GPU to the manufacturer for a replacement.

Some applications, such as Quake 3, crash after querying the OpenGL extension string

  Some applications have bugs that are triggered when the extension string is longer than a certain size. As more features are added to the driver, the length of this string increases and can trigger these sorts of bugs.

  You can limit the extensions listed in the OpenGL extension string to the ones that appeared in a particular version of the driver by setting the `__GL_ExtensionStringVersion` environment variable to a particular version number. For example,

      __GL_ExtensionStringVersion=17700 quake3

  will run Quake 3 with the extension string that appeared in the 177.* driver series. Limiting the size of the extension string can work around this sort of application bug.

XVideo and the Composite X extension

  XVideo will not work correctly when Composite is enabled unless using X.Org 7.1 or later. See Chapter 21, Using the X Composite Extension.

GLX visuals in Xinerama

  X servers prior to version 1.5.0 have a limitation in the number of visuals that can be available when Xinerama is enabled. Specifically, visuals with ID values over 255 will cause the server to corrupt memory, leading to incorrect behavior or crashes. In some configurations where many GLX features are enabled at once, the number of GLX visuals will exceed this limit. To avoid a crash, the NVIDIA X driver will discard visuals above the limit. To see which visuals are being discarded, run the X server with the `-logverbose 6` option and then check the X server log file.

  Please see “How do I interpret X server version numbers?” when determining whether your X server is new enough to contain this fix.

Some X servers have trouble with multiple GPUs

  Some versions of the X.Org X server starting with 1.5.0 have a bug that causes X to fail with an error similar to the following when there is more than one GPU in the computer:

      (!!) More than one possible primary device found
      (II) Primary Device is:
      (EE) No devices detected.

      Fatal server error:
      no screens found

  This bug was fixed in the X.Org X Server 1.7 release.

  You can work around this problem by specifying the bus ID of the device you wish to use. For more details, please search the xorg.conf manual page for "BusID". You can configure the X server with an X screen on each NVIDIA GPU by running:

      nvidia-xconfig --enable-all-gpus

  Please see Bugzilla bug #18321 for more details on this X server problem. In addition, please see “How do I interpret X server version numbers?” when determining whether your X server is new enough to contain this fix.

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