Chapter 7. Frequently Asked Questions
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## Chapter 7. Frequently Asked Questions

This section provides answers to frequently asked questions associated with the NVIDIA FreeBSD x86 Driver and its installation. Common problem diagnoses can be found in Chapter 8, Common Problems and tips for new users can be found in Appendix H, Tips for New FreeBSD Users. Also, detailed information for specific setups is provided in the Appendices.

### 7.1. NVIDIA Driver

| Where should I start when diagnosing display problems?

One of the most useful tools for diagnosing problems is the X log file in `/var/log`. Lines that begin with `(II)` are information, `(WW)` are warnings, and `(EE)` are errors. You should make sure that the correct config file (i.e. the config file you are editing) is being used; look for the line that begins with:

        (==) Using config file:

Also make sure that the NVIDIA driver is being used, rather than the “nv” or “vesa” driver. Search for

        (II) LoadModule: "nvidia"

Lines from the driver should begin with:

        (II) NVIDIA(0)

| How can I increase the amount of data printed in the X log file?

By default, the NVIDIA X driver prints relatively few messages to stderr and the X log file. If you need to troubleshoot, then it may be helpful to enable more verbose output by using the X command line options `-verbose` and `-logverbose`, which can be used to set the verbosity level for the `stderr` and log file messages, respectively. The NVIDIA X driver will output more messages when the verbosity level is at or above 5 (X defaults to verbosity level 1 for `stderr` and level 3 for the log file). So, to enable verbose messaging from the NVIDIA X driver to both the log file and `stderr`, you could start X with the verbosity level set to 5, by doing the following

        % startx -- -verbose 5 -logverbose 5

| I have read that the NVIDIA FreeBSD Driver is not a native driver, but sits on top of the Linux ABI compatibility layer. Is this true?
| No, the NVIDIA FreeBSD Graphics Driver is a native driver. It does provide Linux OpenGL libraries in addition to the native, FreeBSD libraries to enable users to run Linux OpenGL applications.
| Is the NVIDIA FreeBSD Accelerated Graphics Driver thread-safe?
| This release is thread-safe on FreeBSD 7.3 or later systems making use of the libpthread or libthr KSE threading libraries. On these systems, the NVIDIA Linux ABI compatibility libraries are fully thread-safe as well.
| Why can't the Linux compatibility libraries correctly determine if they are used in a multithreaded application?
| The Linux compatibility libraries are not able to correctly determine if they are used in a multithreaded application because the %gs segment register is not initialized correctly for Linux compatibility. The `__GL_SINGLE_THREADED` environment variable (set to "1") can be used to work around this issue, but at the cost of thread-safeness.
| Why does X use so much memory?

When measuring any application's memory usage, you must be careful to distinguish between physical system RAM used and virtual mappings of shared resources. For example, most shared libraries exist only once in physical memory but are mapped into multiple processes. This memory should only be counted once when computing total memory usage. In the same way, the video memory on a graphics card or register memory on any device can be mapped into multiple processes. These mappings do not consume normal system RAM.

This has been a frequently discussed topic on XFree86 mailing lists; see, for example:

http://marc.theaimsgroup.com/?l=xfree-xpert&m=96835767116567&w=2

Note, also, that X must allocate resources on behalf of X clients (the window manager, your web browser, etc); the X server's memory usage will increase as more clients request resources such as pixmaps, and decrease as you close X applications.

The IndirectMemoryAccess X configuration option may cause additional virtual address space to be reserved.

| Why do applications that use DGA graphics fail?

The NVIDIA driver does not support the graphics component of the XFree86-DGA (Direct Graphics Access) extension. Applications can use the XDGASelectInput() function to acquire relative pointer motion, but graphics-related functions such as XDGASetMode() and XDGAOpenFramebuffer() will fail.

The graphics component of XFree86-DGA is not supported because it requires a CPU mapping of framebuffer memory. As graphics cards ship with increasing quantities of video memory, the NVIDIA X driver has had to switch to a more dynamic memory mapping scheme that is incompatible with DGA. Furthermore, DGA does not cooperate with other graphics rendering libraries such as Xlib and OpenGL because it accesses GPU resources directly.

NVIDIA recommends that applications use OpenGL or Xlib, rather than DGA, for graphics rendering. Using rendering libraries other than DGA will yield better performance and improve interoperability with other X applications.

| My kernel log contains messages that are prefixed with "Xid"; what do these messages mean?
| "Xid" messages indicate that a general GPU error occurred, most often due to the driver misprogramming the GPU or to corruption of the commands sent to the GPU. These messages provide diagnostic information that can be used by NVIDIA to aid in debugging reported problems.
| I use the Coolbits overclocking interface to adjust my graphics card's clock frequencies, but the defaults are reset whenever X is restarted. How do I make my changes persistent?

Clock frequency settings are not saved/restored automatically by default to avoid potential stability and other problems that may be encountered if the chosen frequency settings differ from the defaults qualified by the manufacturer. You can use the command line below in `~/.xinitrc` to automatically apply custom clock frequency settings when the X server is started:

        # nvidia-settings -a GPUOverclockingState=1 -a GPU2DClockFreqs=<GPU>,<MEM> -a GPU3DClockFreqs=<GPU>,<MEM>

Here `<GPU>` and `<MEM>` are the desired GPU and video memory frequencies (in MHz), respectively.

| Why is the refresh rate not reported correctly by utilities that use the XRandR X extension (e.g., the GNOME "Screen Resolution Preferences" panel, `xrandr -q`, etc)?

The XRandR X extension is not presently aware of multiple display devices on a single X screen; it only sees the MetaMode bounding box, which may contain one or more actual modes. This means that if multiple MetaModes have the same bounding box, XRandR will not be able to distinguish between them.

In order to support DynamicTwinView, the NVIDIA X driver must make each MetaMode appear to be unique to XRandR. Presently, the NVIDIA X driver accomplishes this by using the refresh rate as a unique identifier.

You can use `nvidia-settings -q RefreshRate` to query the actual refresh rate on each display device.

This behavior can be disabled by setting the X configuration option "DynamicTwinView" to FALSE.

For details, see Chapter 12, Configuring Multiple Display Devices on One X Screen.

| Why does starting certain applications result in Xlib error messages indicating extensions like "XFree86-VidModeExtension" or "SHAPE" are missing?

If your X config file has a `Module` section that does not list the "extmod" module, some X server extensions may be missing, resulting in error messages of the form:

    Xlib: extension "SHAPE" missing on display ":0.0"
    Xlib: extension "XFree86-VidModeExtension" missing on display ":0.0"
    Xlib: extension "XFree86-DGA" missing on display ":0.0"

You can solve this problem by adding the line below to your X config file's `Module` section:

        Load "extmod"

| Where can I find older driver versions?
| Please visit ftp://download.nvidia.com/XFree86/FreeBSD-x86/ (new packages for FreeBSD 7.3 and newer) or ftp://download.nvidia.com/freebsd/ (old i386-only packages for FreeBSD 5.3 through 7.2, inclusive).
| What is the format of a PCI Bus ID?

Different tools have different formats for the PCI Bus ID of a PCI device.

The X server's "BusID" X configuration file option interprets the BusID string in the format "bus@domain:device:function" (the "@domain" portion is only needed if the PCI domain is non-zero), in decimal. More specifically,

    "%d@%d:%d:%d", bus, domain, device, function

in printf(3) syntax. NVIDIA X driver logging, nvidia-xconfig, and nvidia-settings match the X configuration file BusID convention.

The FreeBSD pciconf(8) utility, in contrast, prints and interprets the PCI Bus ID in the format "domain:bus:device.function" (the "domain:" portion is only needed if the PCI domain is non-zero), in decimal. More specifically,

    "pci%d:%d:%d:%d", domain, bus, device, function

in printf(3) syntax.

| How do I interpret X server version numbers?

X server version numbers can be difficult to interpret because some X.Org X servers report the versions of different things.

In 2003, X.Org created a fork of the XFree86 project's code base, which used a monolithic build system to build the X server, libraries, and applications together in one source code repository. It resumed the release version numbering where it left off in 2001, continuing with 6.7, 6.8, etc., for the releases of this large bundle of code. These version numbers are sometimes written X11R6.7, X11R6.8, etc. to include the version of the X protocol.

In 2005, an effort was made to split the monolithic code base into separate modules with their own version numbers to make them easier to maintain and so that they could be released independently. X.Org still occasionally releases these modules together, with a single version number. These releases are simply referred to as “X.Org releases”, or sometimes “katamari” releases. For example, X.Org 7.6 was released on December 20, 2010 and contains version 1.9.3 of the xorg-server package, which contains the core X server itself.

The release management changes from XFree86, to X.Org monolithic releases, to X.Org modular releases impacted the behavior of the X server's `-version` command line option. For example, XFree86 X servers always report the version of the XFree86 monolithic package:

    XFree86 Version 4.3.0 (Red Hat Linux release: 4.3.0-2)
    Release Date: 27 February 2003
    X Protocol Version 11, Revision 0, Release 6.6

X servers in X.Org monolithic and early “katamari” releases did something similar:

    X Window System Version 7.1.1
    Release Date: 12 May 2006
    X Protocol Version 11, Revision 0, Release 7.1.1

However, X.Org later modified the X server to start printing its individual module version number instead:

    X.Org X Server 1.9.3
    Release Date: 2010-12-13
    X Protocol Version 11, Revision 0

Please keep this in mind when comparing X server versions: what looks like “version 7.x” is older than version 1.x.

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