The Linux Gamers' HOWTO
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5. XFree86 and You

If you're going to game under X, it's crucial that you know a bit about X. The "X Window User HOWTO", and especially "man XF86Config" are required reading. Don't short change yourself; read them. They have an extremely high "information to space" ratio. Many problems can be fixed easily if you know your way around XF86Config (or XF86Config-4).

5.1. Getting information about your X system

5.1.1. Probeonly

One of the best diagnostic tools and sources of information about your X system is probeonly output. To use it, kill X if it's already running and from a console, type: 

    X -probeonly 2> X.out

Yes, that's a single dash; so much for standards. The output of X goes to stderr, so we have to redirect stderr with "2>" to a file named X.out. This file will have almost everything there is to know about your X system. It's crucial that you know the difference between the various markers you'll see in probeonly output: 

    (--) probed              (**) from config file    (==) default setting
    (++) from command line   (!!) notice              (II) informational
    (WW) warning             (EE) error               (??) unknown.

Here's an example of some information I gleaned from my output:

I'm running at 16 bpp color:

    (**) TDFX(0): Depth 16, (--) framebuffer bpp 16

X has detected what my videocard chipset and videoram are:

    (--) Chipset 3dfx Voodoo5 found
    (--) TDFX(0): VideoRAM: 32768 kByte Mapping 65536 kByte

5.1.2. Getting info about your setup: xvidtune

xvidtune is your friend when your X screen is shifted a little bit too far to the right, or if the vertical length is too small to fit on your monitor. However, it's a great diagnostic tool also. It'll give you:

5.1.3. Getting info about your setup: xwininfo

xwininfo tells you all sorts of information about X windows. And actually, your "background" or "root" window is considered a window too. So when xwininfo asks you to click on the window you want the information on, click on your background. It'll tell you things like:

: Screen resolution

: Width and Height

: color bpp

: Depth

and a few other things which are interesting but not immediately relevent to our subject, like "Window Gravity State" which tells where new windows tend to be placed by the window manager.

5.1.4. Other sources of information

xdpyinfo gives cool stuff, like X version and loaded extensions (invaluable when trying to see what's missing, like GLX, DRI, XFree86-VidMode, etc.).

5.1.5. Getting information about your 3D system

glxinfo gives lots of useful information about OpenGL (whether direct rendering is being used or not, the currently installed versions of glx and mesa), vendor/renderer strings, the GL library files being used and more.

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Definitions: Video Card and 3D Terminology Various Topics