Casey Bralla on 10 Apr 2010 20:30:52 -0700

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[PLUG] Limit Screen Resolution in X

I've discovered the cause of a persistent series of problems I've been having 
when hacking new installations of Linux and X.   Often I find that the X 
simply doesn't work  (blank screen).  I can run all the correct configuration 
programs and then start X, but all I get is a blank screen.  When I kill X, I 
am left with a normal text screen, and the logs don't indicate anything bad 
happening.  (No errors.  The computer thinks everything was 'hunky', while 
simultaneously being 'dory' too)

This happens most of the time when I use a built-in graphics chip (typically a 
Radeon) of the type that is frequently included on a motherboard.   I had 
always assumed this was do to some goofyness with the way the chips are 
integrated, or a crummy BIOS or something.   My solution has always been to 
install a regular graphics card which almost always worked just fine.

Today, I found the real reason the screen blanks:  The resolution is too high 
for the old CRT monitor on my test bed to display.   Instead of going crazy by 
trying to display a resolution beyond its abilities, the old CRT monitor 
simply shut off the screen (as if there were no video signal at all)

So.... How can I get X to limit its resolution to something "normal" (ie: 

I tried using the "gft" program today and set an explicit modeline in my 
xorg.conf file, but this didn't seem to work.  (Maybe I made a typo or did it 
wrong?)   X has changed recently and apparently doesn't really even need a 
config file when HAL is running, but I'm not knowledgeable of how this works.

Does anybody know an easy way I can limit the screen resolution?   

And how the heck does X even know what the maximum is?  Somehow it gets 
__some__ info (wrong info, in my case), but I don't have a clue how it does 
this.  Anybody want to help educate me (and this list)?



Casey Bralla

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