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The Answer Guy

By James T. Dennis,
Starshine Technical Services, http://www.starshine.org/

Tuning X to work with your Monitor

From Alan Morton on the L.U.S.T Mailing List on 14 Aug 1998

I am wondering if anyone on the list has any experience with a vid card/monitor combination similar to mine, or have any experience with this particular problem that can either give me some constructive advice or can point me to some relevent documentation.

I am using a Jaton 67-P video card with 4 megs of RAM. I am trying to use it with a HP 4033A monitor. The problem is that whem I use Xconfigurator (I'm using a RH5.0 distro) irregardless of what it says about an acceptable configuration, when I start up X it trips the Power Saving function on the monitor and it goes blank.

When I use the cntrl-alt-backspace it naturally kills X, plus it retrips the monitor and my screen begins to reappear. I am making the assumption that it is engaging some error procedure in the monitor, which is fine. But I really want to get this working at a reasonable resolution. If I use a setting of 800x600 and 8 bit color it works just fine, but that seems a bit wasted on a 21" monitor.

I know the monitor will handle a lot because I can use it at 1024x748 in 16 bit color with my Windows NT boot-up. And I have a friend with an identical monitor running 1280x1024 in 24 bit color under Win95.

I don't think the problem is the card because I have been running it with a 14" Magitronic monitor previously at 800x600 in 24 bit under both NT and Linux with no problems.

Any assistance with this will be greatly appreciated.
Alan Morton

The problem you are having is related to the refresh rate that X is trying to use for the mode you are trying to display. The rate may be either too high or too low. I am not sure exactly about the specifics of what needs to be done to change the refresh rate that X uses, but I'm sure there is a good source of information for configuring the display properties of X. Hopefully this will narrow your scope in searching for an answer, because I don't really know what else would cause this problem. Any other suggestion welcome.

Configuring X on a system is like a classic "three-body problem."

You have to get the correct software and libraries all installed (which any distribution makes pretty easy).

You have to select the correct "server" for your video card. This is complicated by the number of video card manufacturers --- many of whom have many models of video card, often identified by a stream of very similar sound digits and letters while using completely different combinations of chipsets, clock chips, and RAMDAC's (digital to analog coverters?).

You have to provide a "tuned" set of video timings. This is primarily dependent on your monitor.

Getting all of these things to work together is still a pain. However, the xf86config, SuperProbe, and Xconfigurator have helped alot. I've heard that Eric S. Raymond's Video-Timings-HOWTO has helped alot of people (though I've never used it myself). I've played with 'vidtune' (an X program that allows you to tune your video times after you've gotten "close enough") --- but it's still a bit mysterious to me. (How to I get it to write the timings out to a format I can use in my XF86Config?)

I usually just use a "hit and miss" approach by looking through the list of samples in /usr/X11R6/lib/X11/doc/Monitors (or thereabouts). The one on my S.u.S.E. box lists about 65 different samples for various monitors. I just play with them a bit while I hand hack on the /etc/X11/XF86Config file (which is probably the least efficient way of doing it --- but usually Xconfigurator and a good multisync monitor get along O.K. so I usually don't have to fuss too much).

Copyright © 1998, James T. Dennis
Published in Linux Gazette Issue 32 September 1998

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