Re: Changing number of colors of XServer
Thanks for the information,
How does the XServer know WHICH Screen section to use? I notice that my file has
several sections labled like this.
Thanks,
Doug
(Ted Harding) wrote:
> On 08-Aug-98 Doug Thistlethwaite wrote:
> > My XServer is currently configured to sue 256 colors. (8 bits). I have
> > noticed that when I start netscape I get messages telling me it can't allocate
> > a larger color map. I figured that if I increased the number of colors, this
> > problem would go away.
> >
> > How do I change the number of colors on my display?
>
> In theory, you figure right. Netscape is colour-hungry and 256 colours is not
> enough if you have other colour-intensive applications running. (You can
> start netscape with the "-install" option to use a "private colormap", but this
> has other side-effects: try "netscape -install &" to see if you can live with
> it; if so, this is a fix for your immediate problem).
>
> Also in theory, changing the number of colours ("colordepth") in X is
> straightforward. You can simply edit the appropriate part of /etc/XF86Config;
> all the necessary keywords are exemplified in the following:
>
> Section "Screen"
> Driver "Accel"
> Device "Primary Card"
> Monitor "Primary Monitor"
> DefaultColorDepth 32
> SubSection "Display"
> Depth 8
> Modes "1024x768" "800x600" "640x480"
> EndSubSection
> SubSection "Display"
> Depth 15
> Modes "1024x768" "800x600" "640x480"
> EndSubSection
> SubSection "Display"
> Depth 16
> Modes "1024x768" "800x600" "640x480"
> EndSubSection
> SubSection "Display"
> Depth 24
> Modes "1024x768" "800x600" "640x480"
> EndSubSection
> SubSection "Display"
> Depth 32
> Modes "1024x768" "800x600" "640x480"
> EndSubSection
> EndSection
>
> Alternatively, run the utility which sets up X: most modern X-configurators
> offer the choice of colour depths and default depth.
>
> HOWEVER: In practice it gets more complicated, in that your video card has to
> be able to cope with the colour depth and resolution you request, and even if
> it can cope it may only do so if you also set certain special options in the
> card-specific XF86Config section. These options may depend not only on the
> generic card model but also on who manufactured it, i.e. different "clones"
> may require different setups. You have to experiment and read the card info in
> the XF86 documentation (look under /usr/X11R6/lib/X11/Cards and
> /usr/X11R6/lib/X11/doc).
>
> That being said, the main factor is the Video RAM on the card. The rule is
> (Horizontal resolution)x(Vertical resolution)x(Bytes for colour depth) bytes
> of RAM _minimum_. (Bytes for colour depth) is, of course, 1 for 8bpp (256
> colours), 2 for 16bpp (65536 colours), and 3 for 24bpp. Paradoxically, 32bpp
> is often implemented as a "packed 24bpp" and may only need 3 bytes per pixel,
> i.e. you may be able to get 1280x1024x32bpp with a 4MB card, even though it
> looks as though you need 5MB.
>
> One complication here is that some cards insist on using half the video RAM as
> a "frame buffer" in which case you may not get what you might think you could
> get. Since X allows a larger "Virtual" screen than appears on the monitor, you
> should use the "Virtual" dimensions in the above calculation if relevant.
>
> The main symptom of a card not being able to cope with the colour depth you
> request is either a lot of fuzzy twinkling garbage, or else the screen image
> being broken up and variously wrapped round (horizontally and/or vertically).
>
> Hope this helps, and I hope it actually proves straightforward!
> Ted.
>
> --------------------------------------------------------------------
> E-Mail: (Ted Harding) <Ted.Harding@nessie.mcc.ac.uk>
> Date: 09-Aug-98 Time: 10:41:34
> --------------------------------------------------------------------
>
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