Re: How to change start up screen resolution for X?

[Ross Boylan <RossBoylan@stanfordalumni.org>]

On Sun, Jan 19, 2003 at 02:49:29AM -0500, Travis Crump wrote:
> nate wrote:
> >Ross Boylan said:
> >
> >>I am looking for a way to get hardware accelerated 3d performance out of
> >>my video card.  For reasons detailed below, this seems to come down to the
> >>need to start X in a lower resolution and depth than I
> >>customarily use.  I am looking for a good way to do that, or the
> >>encouraging news that some other approach is possible.
> >
> >
> >
> >put the mode you wish to use on startup as the first mode. e.g. for my
> >system I use 1600x1200 as my primary modeline, and my
> >/etc/X11/XF86Config-4 has:
> >
> >Section "Screen"
> >    Identifier  "Screen 1"
> >    Device      "Nvidia Geforce3"
> >    Monitor     "Viewsonic PF790"
> >    DefaultDepth 24
> >
> >    Subsection "Display"
> >        Depth       8
> >        Modes      "1024x768"
> >    EndSubsection
> >    Subsection "Display"
> >        Depth       16
> >        Modes       "1024x768"
> >    EndSubsection
> >    Subsection "Display"
> >        Depth       24
> >        Modes       "1600x1200" "1280x1024" "1024x768"
> >    EndSubsection
> >EndSection
> >
> >
> >you should be able to start multiple X servers by doing something like
> >this on the command line
> >
> >startx -- :1
> >
> >though, last time I tried I couldn't figure out a good way to specify
> >a resolution to be used along with color depth on the command line if
> >I wanted it in a different resolution, 
> 
> What I do is just make up a second Section "Screen" in the same 
> XF86Config-4 and give it its own identifier.  When I want to use it I 
> just do:
> 
> startx -- :1 -screen <itsidentifier>
> 
> 
> 

Thanks to both of you for this very helpful information.  I have a
couple other points of information for those who may find this
message, and some additional questions.

It's necessary to omit higher resolutions from the modeline entirely.
For example,
    Modes  "640x480" "1024x768"
starts the screen at 640x480, but this is on a virtual 1024x768
desktop.  X always looks for the biggest size in determining the
virtual desktop size.  (There is a Virtual command in the Display
subsection, but it operates just by knocking out the higher
resolutions).

Second, my card (Matrox Millenium G200) I could not get DRI until I
loaded the agpgart and mga modules.  I only discovered this from the
README at Matrox's site (wonder if I should file a bug, of if I just
missed it).  This seems a little weird, since mga was undoubtedly
loaded by XFree (though it has its own loader, I gather).

My remaining questions or curiosities are, first, whether anyone can
explain why DRI needed this extra help and second, whether there is an
alternative to running startx as root.  When I try it as non-root I
get the error that I don't have permission to start X.  This is
consistent with some of the docs saying only root can start XFree.
But it means I end up with the new session running as root, which is
not a very safe way to play a game!  (For reasons I haven't tracked
down, it starts up an AfterStep session, though it's not my primary
environment).