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Old 09-23-2009, 09:45 AM   #1
Bller
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CentOS 5 problem


I just installed the latest CentOS version from a DVD that was checked after write. The install went well, i did a clean install, erased all my HDD and installed CentOS. But when it finishes and i remove the install DVD and reboot, it tries to enter X, in gnome, but i get an over frequency from my monitor. I guess X chosed a default resolution bigger than my monitor can handle. It can go like 1340 or so but bigger than that it gives me the frequency error. Any thoughts on how to lower the res ?
 
Old 09-23-2009, 10:10 AM   #2
MensaWater
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You can tweak video settings in /etc/X11/xorg.conf.

You can start system in init 3 to keep it from starting X. Make your changes then do init 5 to go into run level 5 to start X to see if it works any better.
 
Old 09-23-2009, 10:14 AM   #3
Bller
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Quote:
Originally Posted by jlightner View Post
You can tweak video settings in /etc/X11/xorg.conf.

You can start system in init 3 to keep it from starting X. Make your changes then do init 5 to go into run level 5 to start X to see if it works any better.
How do you actually enter in init 3 ? I mean how can i change it ? I don`t get any terminal where i could type startx or edit something. The only thing i can do is try to access my system through the recover system from the DVD, there i have a terminal where i could do something,
 
Old 09-23-2009, 10:21 AM   #4
ak@shdubey
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Quote:
Originally Posted by Bller View Post
How do you actually enter in init 3 ? I mean how can i change it ? I don`t get any terminal where i could type startx or edit something. The only thing i can do is try to access my system through the recover system from the DVD, there i have a terminal where i could do something,
Hi Bller,

If you are able to login to gnome sucessfully(despite of bad resolution)
open terminal window (ctrl+alt+f1/f2 will do )
#su - (to become root)
#init 3 (to get to single user mode)


-Akash
 
Old 09-23-2009, 10:54 AM   #5
MensaWater
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When you get the initial screen for boot select the default boot image (usually already highlighted) then hit "e" to drop into menu editing mode. Just add a "3" to the end of the existing boot line it shows and that tells it to boot into run level 3 instead of the default (presumably 5).

The default is specified in /etc/inittab like this:
id:5:initdefault:
You can change that 5 to 3 (after you've booted) so that subsequent boots while you're testing automatically start in run level 3 instead of 5. Don't forget to change it back to 5 when you're done.
 
Old 09-23-2009, 11:59 AM   #6
Bller
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Ok i managed to edit my xorg.conf file something like this :

Code:
Section "Device"
	Identifier  "Videocard0"
	Driver      "vesa"
EndSection

Section "Screen"
	Identifier "Screen0"
	Device     "Videocard0"
	DefaultDepth     16
	SubSection "Display"
		Viewport   0 0
		Depth     16
	EndSubSection
This thing did work, and i`m actually in Gnome. But i`m not satisfied with my default resolution. I thing that the radeon driver didn`t work for me. So i changed the radeon with vesa, and depth from 24 to 16. If i would like to have a bigger resolution available, what should i do?
 
Old 09-23-2009, 12:20 PM   #7
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A non open source driver from ATI may work better than whatever open source driver is included in Centos.

Recently, I've only used non open source drivers from nVidia, so I don't have any current info on downloading and installing them direct from ATI, vs. whatever support might be in Centos.

Dropping the depth from 24 to 16 should only have helped if your video interface were severely short of either ram size or RamDac bandwidth. That is unlikely for anything near current hardware and doesn't fit your initial symptoms.

You may need to find out the maximum horizontal and/or vertical sync rate of your monitor. Typically, those can be interrogated from the monitor by the video driver when X starts, but that process is not always robust. You can put lines in xorg.conf to explicitly set those maximums so the driver will not exceed them.

You may also need a custom mode line in xorg.conf to tell the driver the exact monitor timing you want. There are programs that will compute a custom mode line based on the desired resolution and specified max horizontal and vert sync. (The driver does not compute mode lines. It finds precomputed mode lines in a variety of places and chooses one that fits the specified maximums. That may not be as good as computing an exact fit and providing it in xorg.conf).
 
Old 09-23-2009, 12:40 PM   #8
Bller
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Quote:
Originally Posted by johnsfine View Post
A non open source driver from ATI may work better than whatever open source driver is included in Centos.

Recently, I've only used non open source drivers from nVidia, so I don't have any current info on downloading and installing them direct from ATI, vs. whatever support might be in Centos.

Dropping the depth from 24 to 16 should only have helped if your video interface were severely short of either ram size or RamDac bandwidth. That is unlikely for anything near current hardware and doesn't fit your initial symptoms.

You may need to find out the maximum horizontal and/or vertical sync rate of your monitor. Typically, those can be interrogated from the monitor by the video driver when X starts, but that process is not always robust. You can put lines in xorg.conf to explicitly set those maximums so the driver will not exceed them.

You may also need a custom mode line in xorg.conf to tell the driver the exact monitor timing you want. There are programs that will compute a custom mode line based on the desired resolution and specified max horizontal and vert sync. (The driver does not compute mode lines. It finds precomputed mode lines in a variety of places and chooses one that fits the specified maximums. That may not be as good as computing an exact fit and providing it in xorg.conf).
I have like H: 48.3 KHz and V : 59.9Hz sync on my monitor. And it supports a bit more higher than 1280x1024. After that, it goes over frequency. So should i try and change the driver from vesa, back to radeon as it was in the default xorg.conf, and the depth from 16 back to 24, and try adding a new line with the maximum v and h sync and res?
If so, could you give me an example of that sort of xorg file already editted please ? Or tell me some programs that help me do the xorg.conf correctly?
 
Old 09-23-2009, 03:45 PM   #9
johnsfine
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Quote:
Originally Posted by Bller View Post
So should i try and change the driver from vesa, back to radeon
I did not suggest that.

I don't happen to remember the ati driver naming conventions (whatever is comparable to using "nv" for the open source nVidia and "nvidia" for the non open source). Maybe some other expert here will answer.

I also never knew what support Centos might provide for non open source drivers. I use the non open source nvidia driver on Mepis and Mepis provides support for that driver that is better than using the generic installer from nVidia. But I have also tried the generic driver installer from nVidia and it also works.

You could download the generic Linux driver installer from ATI. That is supposed to work OK on any Linux (same on Centos or Mepis or whatever). Start at
http://support.amd.com/us/Pages/drivers.aspx
Then select the driver family, then select the OS (Linux) and architecture (x86 or x86_64) etc.

If Centos has some specific support (other experts please jump in here) for the non open source driver, using that may give results that are easier to maintain through subsequent kernel upgrades than using the version direct from ATI. But the version direct from ATI should work and at worst need to be reinstalled after any kernel upgrade.

Quote:
If so, could you give me an example of that sort of xorg file already editted please ?
There are many other threads at LQ containing samples of xorg.conf files that specific max sync rates and/or provide exact mode lines. I don't remember the exact syntax myself without finding an example. Maybe I'll find one for you later or maybe you'll have it already by then.

I think an exact mode line will be good enough to solve your problem even using the vesa driver. The non open source driver probably will have speed advantages and maybe other advantages and might or might not also need the same exact mode line.
 
Old 09-24-2009, 08:03 AM   #10
Bller
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I installed the proprietary driver and works fine now. Thank you for the tips
 
Old 09-24-2009, 08:08 AM   #11
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if your problem is solved, please mark the thread as solved
 
  


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