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Probing for Dot Clocks
The XFree86 X server has a special probeonly mode that outputs values from the XF86Config file and values it detects. You need to run X in this mode to see if things are going to work and to see if it detects any problems.
Run the command line:
X -probeonly
when your system has no extra load on it. Stop any unneeded programs before running this, as any extra system load may influence the timings X obtains.
The following command runs X in probeonly mode and sends the output to the file named /tmp/x.values:
X -probeonly > /tmp/x.values 2>&1
Be sure to run X from the console. Don’t try to run X if you’re already running X.
If you have some dot clocks in the XF86Config file, then X -probeonly won’t try to detect new ones. Because of this, the first time you run X this way, you should comment out the clocks in your XF86Config file. After you run X in probeonly mode, you can add the clocks to the XF86Config file and try it again, seeing if things still seem to work.
You can then look at the file /tmp/x.values, which should contain something like the following:
XFree86 Version 3.1.1 / X Window System
(protocol Version 11, revision 0, vendor release 6000)
Operating System: Linux
Configured drivers:
S3: accelerated server for S3 graphics adapters (Patchlevel 0)
mmio_928, s3_generic
(using VT number 7)
XF86Config: /usr/X11R6/lib/X11/XF86Config
(**) stands for supplied, (-) stands for probed/default values
(**) Mouse: type: Microsoft, device: /dev/ttyS0, baudrate: 1200
(**) S3: Graphics device ID: "Actix GE32+ 2MB"
(**) S3: Monitor ID: "NEC MultiSync XE17"
(**) FontPath set to
"/usr/X11R6/lib/X11/fonts/misc/,/usr/X11R6/lib/X11/fonts/Type1/,/usr/X1
1R6/lib/X11/fonts/Speedo/,/usr/X11R6/lib/X11/fonts/75dpi/,/usr/X11R6/li
b/X11/fonts/100dpi/"
(-) S3: card type: ISA
(-) S3: chipset: 928, rev E or above
(-) S3: chipset driver: mmio_928
(**) S3: videoram: 1024k
(**) S3: Ramdac type: att20c490
(-) S3: Ramdac speed: 110
(-) S3: clocks: 25.24 28.32 39.99 0.00 50.13 77.02 37.35 44.89
(-) S3: clocks: 90.11 119.98 80.30 31.50 110.16 65.08 75.17 94.68
(-) S3: Maximum allowed dot-clock: 110.000 MHz
(**) S3: Mode "1024x768": mode clock = 81.000, clock used = 80.300
(**) S3: Mode "800x600": mode clock = 50.000, clock used = 50.130
(**) S3: Mode "640x480": mode clock = 31.000, clock used = 31.500
(-) S3: Using 6 bits per RGB value
(**) S3: Virtual resolution set to 1024x768
Note that many of these values come from our XF86Config file.
Now, add the clocks to the Device section of your XF86Config file. Note that each time we ran X -probeonly, it returned slightly different clock values. For example, in this run, we got the following clock values (formatted for the XF86Config file):
Clocks 25.24 28.32 39.99 0.00 50.13 77.02 37.35 44.89 Clocks 90.11 119.98 80.30 31.50 110.16 65.08 75.17 94.68
From the AccelCards file, we found these clocks—close, but not exact:
Clocks 25 28 40 72 50 77 36 45 Clocks 90 120 80 32 110 65 75 95
Now you’re ready to start X and see if things work. Type in the following command and see if things start up:
startx
The startx shell script is the official way to start X from a user account.
The startx script runs the xinit program, which does two things: runs the X server (the program named X) and then runs the commands in the .xinitrc file in your home directory. These commands should set up the X applications you want launched on startup. If there’s no .xinitrc file in your home directory, then xinit runs a default script. The system default .xinitrc file is /usr/lib/X11/xinit/xinitrc.fvwm (no dot).
The best way to start out with X is—once you verify your XF86Config file—to copy the system .xinitrc into your home directory and then edit this file. Most of the .xinitrc file comes from the standard XFree86 installation for Linux; it looks for certain files, few of which will actually exist, and it executes programs using those files it finds. The section at the end is where you’ll set up the X applications you want started when X starts.
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