From: "Ryan Gray" <[EMAIL PROTECTED]>
Subject: [XFree86] Support
Date: Mon, 3 Mar 2003 01:00:49 -0500
Hi Ryan,
the problem you described results from the following conflict: The
monitor (and in principle the video card also) you use has a upper
limit for the vertical and horizontal refresh rates.
The values for this rates are a result from the so called "modes":
These modes describe, what resolution you want to use with your
monitor.It also determines, how many times the picture on your
monitor is redrawn. Values below 75Hz may result in a flickery screen
here.
Example:
It is obvious, that a screen of 640x480 pixels (picture cells or
simply "dots") can be redrawn much more often as for example a screen
of the resolution of -- say -- 1280x1024 "dots". That is: The
vertical refresh rate ("pictures/screens per second") is very high in
the first and very low in the second example.
IF you would configure XFree in a way that it instructs the video
card to generate VGA signals for a 1280x1024 dots screen to be
redrawn 200 times per second and the monitor could only survive 70
screens of the resolution per second -- you will get a fried high
voltage transformator of the monitor.
That is, why there is an upper (and lower) limit given in the
XF86Config file for your monitor.
All modes which will exceed that limits are silently skipped to save
the life of your monitor.
Fortunatley nowadays monitors will switch off, if feed with a "too
fast" signal...but old monitors will be probably changed into a fried
tomatoe. ;)
To solve the problem:
Try to figure out what horizontal and vertical limits are given for
the monitor you want to use -- this may be an entry in the users
manual.
In the XF86Config file (probably as /etc/X11/XF86Config) edit the
following entries accordingly (THIS IS ONLY AN EXAMPLE FROM THE
XF86CONFIG FILE I USE FOR MY MONITOR!!! DONT COPY THAT VALUES!!! USE
YOUR OWN !!!)
------------------------------------------------------
Section "Monitor"
Identifier "MF-8617A"
# HorizSync is in kHz unless units are specified.
# HorizSync may be a comma separated list of discrete values, or a
# comma separated list of ranges of values.
# NOTE: THE VALUES HERE ARE EXAMPLES ONLY. REFER TO YOUR MONITOR'S
# USER MANUAL FOR THE CORRECT NUMBERS.
HorizSync 27-86 <<<------!!!----------
# VertRefresh is in Hz unless units are specified.
# VertRefresh may be a comma separated list of discrete values, or a
# comma separated list of ranges of values.
# NOTE: THE VALUES HERE ARE EXAMPLES ONLY. REFER TO YOUR MONITOR'S
# USER MANUAL FOR THE CORRECT NUMBERS.
VertRefresh 50-120 <<<------!!!----------
Gamma 1.0 1.0 1.0
EndSection
------------------------------------------------------
Now skip to the "Screen" section and take a look at it. The entry
"Modes" will tell XFree what resolutions to use first. Comment this
line out (use "#"), copy it (remove the "#" at the start of the copied
line....:) and remove every resolution setting but the lowest
resolution (its a test). Store that file again.
------------------------------------------------------
Section "Screen"
Identifier "Screen 1"
Device "radeon"
Monitor "MF-8617A"
DefaultDepth 24
Subsection "Display"
Depth 24
Modes "1280x1024" "320x240" <<<<-------!!!-------
ViewPort 0 0
EndSubsection
EndSection
------------------------------------------------------
Now, activate a terminal (use SHIFT-ALT-1), login as root and switch
to runlevel 2 ("telinit 2"), wait until all has settled down, check
whether X, gdm and such is still running (it should not...but) and
kill those tasks per hand, if not.
Swicth to runlevel 5 ("telinit 5") again.
You should get a X session with a very low resolution now.
Try to modify the resolution setting in the "Screen" section of the
XF86Config file to higher values (dont use fantastic value like
507x396 dots! ;)
Common values are:
"1280x1024" "1024x768" "800x600" "640x480"
At a certain resolution you will get "your problem" again: This is a
resolution, your monitor cannot display without exceeding the limits
for the hoprizontal and vertical refresh rates then.
Additional informations you will get by reading the
/var/log/XFree86.0.log file (or similiar). Here all skipped resolution
("modes"-) settings are listed.
Hopefully this will clearify the situation a little bit, Ryan.
Dont hesitate to mail me !
Keep hacking!
Meino
> Hello,
>
>
>
> I have just tried to install Red Hat Linux version 8.0 and it installs
> properly but when I reach the command prompt after a seemingly
> successful installation I get the error:
>
>
>
> (EE) VESA(0): No matching modes
>
> (EE) Screen(s) found but none have a usable configuration
>
>
>
> Fatal server error.
>
> No screens found.
>
>
>
> I have tried installing multiple times and booting with different
> monitors, the monitor I was originally using couldn't be identified
> during the probe so I hooked up another one that was successfully
> probed, but the end result is still the same.
>
>
>
> I know that the CD's work because they have successfully installed the
> os on a friends computer with no complications.
>
>
>
> Any help you could offer is much appreciated.
>
>
>
> Thanks,
>
> Ryan Gray ([EMAIL PROTECTED])
>
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